Computer tech Liam Cooper arrived in Los Angeles following the death of his mother, Kelly Cooper, who said he could find his father at design house Forrester Creations. Both Thorne Forrester and publishing magnate Bill Spencer, Jr. had dated Kelly, so they submitted to a DNA test; Liam chafed when the more aggressive Bill turned out to be his father. Liam made the adjustment with the help of Hope Logan, which led to a sweet romance, during which Liam fended off the advances of Hope's rival, Steffy Forrester.

After a misunderstanding with Hope, Liam got drunk at a party and hit his head, waking up next to Amber Moore, who soon claimed she was carrying Liam's baby. Liam and Hope went through a dizzying array of breakups and makeups trying to decide what was best for the child, and Liam faced competition from Hope's ex-boyfriend, Oliver Jones. Liam suffered a concussion in an explosion caused by Amber's pilot light; months later, Liam realized he'd been duped when Amber gave birth to an African-American baby, barely stopping Hope from accepting Oliver's marriage proposal.

When Hope wanted to stay a virgin until her wedding night, Liam became frustrated and publicly proposed to Hope during a showing for her Hope for the Future fashion collection. Liam saved Steffy, who fell in her bathtub and nearly drowned; Liam resisted when Steffy became amorous and let him know she was sexually available. After Liam kissed Steffy and came home to find Hope's engagement ring on his mantel, Liam gave the ring to Steffy and took her to Aspen, exchanging vows with her there during a surprise wedding.

Liam later found out that Hope had seen him kissing Steffy but followed him to Aspen to make things right, only to be locked in a gondola by a disapproving Bill and forced to watch Liam's wedding. Liam wanted to return to Hope but felt obligated to stay with Steffy, who was suffering from a life-threatening blood clot as the result of being thrown from an ATV in Cabo San Lucas. Though Liam forgave Steffy for conspiring with Bill in Aspen, Liam raged upon learning Bill had faked Steffy's MRI to manipulate him into staying with Steffy. Liam asked Steffy for an annulment and was about to marry Hope until Steffy announced she wanted to hold out for a proper divorce.

Liam moved Hope in with him, but was concerned when she became increasingly erratic after freezing up in bed. Liam saved Hope from drowning in the Forrester pool, upset to find she'd been taking excessive doses of antianxiety pills so she could make love to him. After Hope crashed into Steffy on the slopes of Aspen, the furious Liam tended to Steffy and tore up the annulment papers she'd finally agreed to sign.

About to marry Hope in Puglia, Italy, Liam found a note from the absent Hope which declared she couldn't go through with it. Liam professed his love to Steffy, relenting when Hope explained she had been delayed by the sudden appearance of her estranged father, Deacon Sharpe. Liam finally married Hope, but after she saw a video of him kissing Steffy he'd accidentally taken with his iPad, Liam agreed to give Hope a "do-over" wedding. But Liam partied with Steffy the night before and showed up for Hope's ceremony with dyed hair and a temporary tattoo, so Liam found himself single again, soon finding his way back to Steffy.

Liam raged to learn that Hope's brother, Rick Forrester, had told Hope that Liam kissed Steffy before the do-over, and that Bill broke Deacon out of jail to ruin the Puglia wedding. Liam punched Rick and disowned Bill, relenting when Bill stabbed himself with his sword necklace; Liam didn't know Bill cushioned the blow with his money pouch. When Hope wanted Liam back, Liam asked for time to think but walked into a surprise wedding that Steffy interrupted with news she was pregnant. Liam married Steffy instead in a unique ceremony where she roared down the aisle on a motorcycle; Liam asked Steffy to stop riding until after the baby was born and was inconsolable when Steffy had an accident and miscarried. Liam questioned why Steffy suddenly moved to Paris until he followed her there and learned that the accident had left her barren.

Liam tentatively moved on with Hope, who was also seeing Wyatt Fuller. Liam was shocked to learn that Wyatt was his half-brother through a fling Bill once had with Quinn Fuller, but that didn't stop Liam from punching Wyatt for kissing Hope. Liam scrambled to explain when Hope saw a video tribute Liam made for Steffy, realizing Quinn had hacked into his e-mail in an attempt to push Hope toward Wyatt. Getting Hope down the aisle, Liam was surprised when Steffy arrived, telling him she could have children again thanks to a procedure she had done overseas. Liam wished Steffy well but had to follow Hope to Hawaii when she ran off with Wyatt; though Liam explained Quinn had convinced Steffy to see him, Liam flew home alone.

When Liam found security footage that showed Wyatt pocketing the rare "Hope for the Future" diamond he said he'd rescued from jewel thieves, Liam crashed Hope's camping trip with Wyatt and exposed him, but only after he managed to escape being trapped in an elevator by Quinn. Liam cringed when he came upon houseguest Bill having raucous S&M sex with Quinn. Later, after hearing about Hope's pregnancy scare, Liam lured Hope into Wyatt's camper and drove off, trying to convince Hope to date both of them. Having been locked in the Forrester steam room by Quinn, Liam won Hope when Wyatt socked him for calling Quinn an evil bitch.

Liam barely survived when Quinn stabbed him with his sword necklace, then tried to impale him with the real thing. Though Liam was grateful to Wyatt for saving him, their brief truce ended when Wyatt presented Hope with the HFTF diamond at a press conference. Liam walked out on Hope, but agreed to meet her in Paris to get married under the Eiffel Tower. En route, Liam was delayed saving jewelry designer Ivy Forrester, who had fallen into the River Seine. After Hope married Wyatt instead, Liam learned Quinn had pushed Ivy into the Seine on purpose, but Hope decided to stay with Wyatt because she was carrying his baby, so Liam moved on with Ivy during a romantic trip to Amsterdam and talked to Ivy's father, John Forrester, about his intentions. Liam found the pregnant Hope at the bottom of a staircase after she argued with the obsessive Quinn; Liam and Hope admitted they'd always love each other after Hope miscarried and decided to move to Milan.

Enraged that new Forrester CEO Rick was tormenting Ivy, Liam devised a takeover plot involving his father's 12.5% stake in the company, but Steffy would only contribute her 25% if Liam came back to her. Instead, Liam worked with Wyatt and found out that Rick's mistress, Maya Avant, was transgender; Liam and Wyatt were aghast when Bill published an exposé on Maya over the brothers' objections. Liam became vice president of Forrester when his plan to combine Bill's stock with that of Steffy's family was successful.

Just as Liam's feelings for Steffy resurfaced, Liam agreed to marry the Australian Ivy, who was facing deportation, in name only. Though Ivy's cousin, Aly Forrester, who had a history of mental illness stemming from the traumatic death of her mother in childhood, died in a violent confrontation with Steffy, Liam dumped Ivy at Aly's memorial. Liam defended Steffy against Ivy, who was trying to blackmail Steffy with a video that made it seem Steffy had killed Aly. After Liam brokered a truce between the feuding cousins, Liam stumbled upon information that his own cousin, Caroline Spencer, was not carrying the child of her husband, Ridge Forrester, but Liam agreed to keep quiet.

Liam withdrew from Steffy as she insisted on telling Wyatt that new girlfriend Ivy was kissing her brother, Thomas Forrester, behind Wyatt's back; though Liam had rebuffed Ivy's attempt at a reconciliation, Liam walked out on Steffy after her battles with Ivy left Ivy electrocuted and suffering from a concussion. Liam suffered his own concussion when he escorted the departing Ivy onto her plane and hit his head in its lavatory; when Liam came home dizzy from his inadvertent flight to Australia, he found Steffy cuddling in bed with Wyatt and broke off his engagement to her without explaining why.

Collapsing in the Forrester parking lot and sustaining another head injury, an amnesiac Liam woke up in a cabin to find Quinn taking care of him. Believing Quinn's story that they were married couple Adam and Eve, Liam made love to Quinn and told her he loved her as she confided in him about her neglectful mother and once losing a child. Though happy with "Eve," Liam wanted to know more about their life together, finding answers in a photo album that displayed doctored wedding photos. Liam began having memory flashes of Steffy; just as Liam was about to travel the world with Quinn, Wyatt rushed in, which gave Liam total recall. Liam escaped when Wyatt helped him lock Quinn in a closet, but Liam was stunned to learn that Steffy had married Wyatt in his absence.

Liam had Quinn arrested, but dropped the charges when Quinn's attorney reminded Liam his sexual relations with Quinn had been consensual and that it would be nearly impossible to make his case stick. Liam bristled when Bill demanded he respect Wyatt's marriage to Steffy, but Liam cried foul when he discovered a secret love nest Bill had created to cheat on Katie with Katie's sister, Brooke Logan. Horrified Liam tried to warn Steffy's grandfather, Eric Forrester, about Quinn when Eric and Quinn became involved. Liam felt encouraged when Ridge confided that he had a plan to get rid of Quinn, but was confused when Ridge later abandoned it.

Though he was briefly intrigued by Ivy, who had come back from Australia sporting sexier clothes and an American accent, Liam took Steffy back after her marriage to Wyatt imploded. Frustrated by Eric and Quinn's ploy to reunite Steffy and Wyatt, Liam nearly left town until Steffy told him she'd fast-tracked her divorce. Liam married Steffy in Sydney, Australia, and watched Steffy zip-line into the ceremony.

Liam figured out that Bill wanted to bulldoze Spectra Fashions, which was being revived by young Sally Spectra, and that his father had ghost-written a scathing review of Sally's work to facilitate it. Though he knew Steffy disapproved of Sally and her relationship with Steffy's brother Thomas, Liam told Steffy about Bill's scheme, which resulted in Thomas investing $100,000 in Spectra to save it from the wrecking ball and defecting to Spectra. Liam liked Sally's spunk and tried to get Steffy to ease up on her.

Liam put his former I.T. skills to use when Eric left Quinn and disappeared with his former wife, notorious criminal Sheila Carter. Having been told by Quinn that Sheila had a gun in her purse, Liam shouted out when Sheila seemed to reach for it and stood shocked as Steffy pulled out her own gun and shot Sheila. Liam helped cover up that crime, but not the one which saw Bill setting fire to Spectra to make way for his building. Liam recorded Bill's confession and forced Bill to step down from Spencer Publications after Bill punched him in the face. Now CEO of Spencer, Liam bought the burned-out Spectra building and gave it to a grateful Sally. Liam stood his ground with Bill and rejected Steffy's attempts to heal the rift between them, causing a rift of their own. After Bill found a way to delete Liam's recording, Liam returned the CEO seat to his father.

Learning that Bill was getting ready to demolish Spectra, Liam arranged a sit-in with Sally and her staff, becoming trapped in the rubble with her after her employees ran scared. Afraid he would die, Liam let Sally kiss him; after being rescued by Bill and Steffy, Liam told Steffy about Sally's kiss and watched Steffy walk out. Once Steffy came home, Liam surprised her with a vow-renewal ceremony and was overjoyed to learn Steffy was pregnant. But when Liam found paternity test results in her purse, he got Steffy to admit she had slept with Bill, prompting Liam to quit his marriage and Spencer Publications.

Liam was glad to have Hope's support after she returned from Milan, and took Hope up on her offer to handle the philanthropic aspects of her Hope for the Future line at Forrester. Liam ignored Steffy's apologies and presented her with annulment papers, suggesting she and Bill were a better fit for each other. Still, Liam rallied at Bill's bedside when Bill was shot by an unknown assailant. Liam agreed to see Steffy but hit his head on a tree branch outside her house, triggering memory flashes in which Liam saw himself putting a bullet in his dad. Liam confessed to Bill, but Steffy helped him see that he'd simply had a revenge fantasy while unconscious from his most recent concussion.

Liam finally forgave Steffy for her night with Bill, but proposed to Hope when Wyatt told him Bill was still carrying on with Steffy. At the altar, Liam was stunned when Wyatt announced he'd found out Bill and Steffy's continuing "affair" was only a ruse, and understood when Hope wanted to postpone their wedding. Liam was at Steffy's side when she gave birth to their daughter, Kelly, whom Steffy had named after Liam's deceased mother. Liam became confused when Steffy seemed to stall on setting a wedding date; by the time Steffy came around, Liam learned that Hope was pregnant with his baby. Liam planned to make a life with Steffy and Kelly anyway, but when Steffy caught Liam kissing Hope, he was stunned to see Steffy removing her engagement ring and putting it on Hope's finger, essentially proposing to Hope on Liam's behalf.

Liam tried to help find the person who was posting threatening comments on the Hope for the Future web site he'd designed. Liam finally married Hope, only to learn Brooke and Taylor had gotten into a fight during the reception and hurled wedding cake at each other. Liam supported Hope through a miscarriage scare, then agreed to Hope and Steffy's idea that the three of them work to create a blended family with his two children. Later, Liam caught an increasingly unstable Taylor accusing Hope of stealing Steffy's life; Liam felt he had no choice but to tell Hope that Taylor had actually been the one to shoot Bill, with Hope wanting Liam to keep Taylor away from the babies.

Liam was excited to go to Catalina Island with Hope for a "babymoon", but had to take a separate flight because Kelly was under the weather. Learning Hope had gone into labor, Liam got frustrated not being able to fly to Catalina during a wind storm via conventional means, so Liam called on Bill to have him flown there in a Spencer helicopter. When Liam arrived, he learned that Hope had miscarried his baby. Liam's attempts to console Hope were unsuccessful; Liam worried when Hope only found peace while holding Phoebe, an infant whom Steffy had just adopted as a sister for Kelly. Liam stood up for his marriage to Hope when she continually insisted he should leave her for Steffy and be a father to both of Steffy's daughters.

Liam suffered another blow when cousin Caroline died from a sudden blood clot. Liam supported Thomas when he came home with Douglas, his son with Caroline; Liam was glad that Hope found solace with the motherless Douglas. Despite knowing Thomas was making moves on Hope, Liam reluctantly agreed to give Hope the annulment she kept asking for. Liam took the guest room at Steffy's; though he mourned his marriage to Hope, he did enjoy co-parenting the children with Steffy. Liam grimaced his way through spending time with Thomas at a party, during which Liam found himself becoming increasingly carefree and amorous. Liam woke up after having made love to Steffy, and felt compelled to tell Hope what had happened.

Liam failed to talk Hope out of marrying Thomas; after the ceremony, Liam overheard Thomas threatening Florence Fulton, Hope's newfound cousin, about a secret concerning Hope. Knowing Flo was Phoebe's birth mother, and Wyatt's girlfriend, Liam recruited Wyatt to get intel from Flo and scratched his head to hear Flo had oddly said she'd never given birth. Liam believed little Douglas when he insisted he'd heard his father saying Phoebe was really Liam's daughter, Beth; after learning from the hospital on Phoebe's birth certificate that Flo had never been a patient there, Liam confronted Flo and learned that she'd helped Reese Buckingham, an obstetrician who stole Hope's baby, switched it with a dead one, and used money from its adoption to pay gambling debts.

Liam got Hope alone and tried to tell her their daughter was alive; when Thomas dragged Hope away, Liam got into a fistfight with him which ended with Thomas confirming Phoebe was really Beth and that he'd known for months but married Hope anyway. Liam and Hope had a joyous reunion with Beth as well as the daunting task of telling Steffy that the baby she'd been raising belonged to Hope. Liam supported Hope's choice to get an annulment from Thomas, who fell off a cliff after a scuffle with Hope and Brooke. Liam worried about the influence Thomas might have if he recuperated on the same property as Hope.

Liam decided to take Bill up on his offer to rejoin Spencer Publications, but fretted when Hope seemed preoccupied with Douglas, whom Hope wanted to adopt in Thomas' absence. Liam was willing to help raise Douglas but didn't think adoption was necessary. Liam didn't like it when Hope suddenly started spending time with both Douglas and Thomas. When Hope began working with Thomas on a Hope for the Future fashion showdown, Liam asked Steffy to help him expose the real reason Thomas was designing for Hope, but the plan went nowhere.

During another confrontation with Thomas, Liam was horrified to hear Thomas brag that Liam was looking at his executioner. Liam reported the threat to Hope and Steffy, only to be frustrated when Thomas downplayed it. Liam proposed to Hope, but made the stipulation that Hope had to give up custody of Douglas. When Hope refused, Liam stayed in Steffy's guest room; while talking to Steffy outside, Liam was surprised when Steffy suddenly kissed him, which Hope saw. Liam took responsibility for the kiss but didn't believe, as Brooke did, that Thomas had arranged for Hope to witness it. Later, Liam kissed Steffy again on his own, feeling he had to show Steffy his heart. Liam was in doubt when Thomas appeared to move on with Reese's daughter, Zoe Buckingham.

Liam reeled when Steffy admitted that Thomas had indeed engineered the kiss that Hope saw. At Thomas' wedding to Zoe, Liam teamed up with her, Hope, and Steffy in an exposure plot that included Hope arriving in a wedding dress Thomas had designed for Hope. After Thomas threw Zoe over for Hope, Liam helped confirm to all in attendance that Thomas had used everyone in his quest to bag Hope. Liam watched as Thomas ran out of his wedding, then planned an impromptu, symbolic ceremony with Hope which saw them exchanging vows in "Bride" and "Groom" T-shirts with Douglas as officiant.

Liam was ready to help when Steffy's motorcycle collided with Bill's car, putting her in the hospital, and cared for Kelly with Hope as Steffy recuperated. Liam couldn't understand why Steffy was becoming increasingly adversarial, to the point Steffy accused Liam and Hope of keeping Kelly from her and pulled a knife on them. Liam found Steffy unconscious and discovered a bottle of painkillers she kept hidden between couch cushions. Though Liam blamed Steffy's doctor, John "Finn" Finnegan, for missing Steffy's addiction because he was infatuated with her, Liam organized an intervention for Steffy with Finn and Ridge and got Steffy into rehab. Liam disapproved of how close Steffy and Finn were getting until Hope pointed out that Liam might be jealous; Liam agreed to back off and stay out of Steffy's personal life.

Liam tried to understand when Hope wanted to forgive Thomas for Douglas' sake and followed by reinstalling Thomas on the HFTF line, but Liam became frustrated when no one would listen to Liam's concerns about Thomas, not even after Liam discovered a life-sized mannequin of Hope in Thomas' apartment. Upset that Hope had brought Douglas to Thomas' for dinner, Liam rushed over and saw Thomas kissing Hope, which sent him to Steffy's to drown his sorrows, and Liam and Steffy made love. Liam reeled when he learned that the unwell Thomas had been kissing the mannequin and that Steffy was pregnant, and not sure if Liam or Finn was the father. Liam repeatedly begged Hope for forgiveness; however, his marriage ended up on even shakier ground when a paternity test revealed Liam had fathered Steffy's child.

Liam couldn't believe it when it turned out Thomas' friend, Vinny Walker, had tampered with Steffy's test; Steffy was actually carrying Finn's baby. Instead of helping to repair things with Hope, the news led Liam to admit he had told Steffy he loved her the night he was unfaithful, and Liam reluctantly granted Hope's request for a separation. Getting to drive Bill's fanciest car, Liam hit something in the road and was so shocked to see it was Vinny that he fainted on the scene. Liam woke up in the passenger seat, horrified that Bill had left Vinny for dead and gotten rid of Vinny's wallet and phone. The haunted Liam wanted to come clean, but gave in to Bill's demands to keep quiet for fear the police would think Liam ran Vinny down on purpose. Liam was spooked when he heard a voice behind him declaring he was under arrest; however, it was only Forrester security guard Charlie Webber playing a prank on him.

Liam was overjoyed when Hope asked him to move home. But his happiness was short-lived when he found himself facing questions by the police. Despite constant demands from Bill to remain quiet, Liam confessed his guilt to Hope and was arrested after he turned himself in. Liam learned that Bill had been jailed as well and shared Bill's confusion when it seemed Bill's lawyer and right-hand man, Justin Barber, was dragging his heels on their defense. Just as Liam was about to be transferred to a maximum security prison, Liam was freed when evidence surfaced that Vinny had thrown himself in front of the car on purpose in an effort to frame Liam and clear the way for Thomas to be with Hope. Liam shared Bill's dismay when he learned that Justin had tried to keep him and Bill in jail so he could control Spencer Publications.

Liam received a shock when Hope invited Deacon, who had just been released from jail for shooting at Quinn, to their home. Liam couldn't believe that Hope had been secretly writing Deacon the entire time he was in prison and didn't want Deacon anywhere near Hope or Beth. Liam listened carefully as Bill warned him to protect his family, however, after Liam had a good talk with Deacon, Liam backed off his hostility towards him. Liam couldn't understand it when Douglas kept insisting that he had seen “Grandma kissing Santa Claus,” but soon Liam learned that Douglas had seen slipped alcoholic Brooke kissing Deacon in a Santa hat on New Year's Eve. Liam joined Hope in offering support to Brooke, who repeatedly berated herself out of guilt when Ridge left her.

Liam was devastated when Steffy and Finn were shot during a robbery, after which Finn died from his injuries. Liam kept vigil at the unconscious Steffy's bedside, but was flabbergasted when Steffy woke up thinking that Liam was her husband. With Steffy still in critical condition, Liam suggested to Hope that, for the time being, they let Steffy continue believing she was married to Liam, but soon Steffy was well enough to handle the truth, so, with Steffy's family at his side, Liam gently told Steffy about Finn's death. Liam continued to spend extended time with the grieving Steffy until she took an extended trip to France.

Liam was surprised to learn that the usually indifferent Bill had brought a mute homeless woman back to his house. Curious, Liam visited Bill and identified the woman as Finn's adoptive mother, Li Finnegan; Liam's presence gave Li total recall, which led to Liam learning that Finn was alive and being held by Finn's biological mother, Sheila, who had shot Finn and Steffy. Later, Liam supported Hope when Thomas wanted to revisit their joint custody of Douglas. As Thomas kept Douglas for an extended sleepover, which forced Hope to visit Douglas at Thomas' home, Liam began to worry that Thomas' obsession with Hope was starting up again; Liam also commiserated with Brooke, whose marriage to Ridge was ruined by a call to Child Protective Services about Douglas that Brooke swore she didn't make. Liam wasn't surprised when the truth came out that Thomas had faked the call with a voice-sampling app to push Ridge toward Taylor.

Liam was appalled when Bill became romantically involved with the psychotic Sheila, but was unable to talk any sense into his father despite repeated attempts. The most Liam could get out of Bill was that Sheila would pay if Sheila were to betray Bill. Meanwhile, Liam scoffed when Thomas went into therapy and was upset that Steffy and Hope wanted the ousted Thomas to return to Forrester to work on Hope's failing Hope for the Future line. Though he heaved a sigh of relief when Hope agreed not to rehire Thomas, Liam freaked when Hope revealed that she'd changed her mind and believed that Thomas had changed. Liam went to both Steffy and Thomas for reassurance, unhappy when Thomas said he would rebuff Hope if she came on to him; Liam began to wonder if Hope had feelings for Thomas that led to continually giving Thomas chances. Liam breathed easier after Bill revealed that he had only been romancing Sheila to goad her into confessing to a long-ago murder.

Though Liam had declined to accompany Hope to Rome for a Hope for the Future showing, Liam thought better of it and traveled to Italy anywhere, where he caught Hope kissing Thomas. Liam reacted by kissing Steffy. After Hope blamed her actions on Liam's heart constantly being divided between her and Steffy, Liam signed divorce papers with Hope. Liam kissed Steffy a second time but was rebuffed by Steffy and clashed with Finn when Liam's feelings for Finn's wife became obvious. Meanwhile, Liam dragged his heels on actually filing for a divorce. When Steffy left town after a free Sheila began coming around for Finn again, Liam called Steffy and asked her to come home -- to him. Though Liam continued trying to convince Steffy that she'd be better off leaving Finn for him, on one such day he also told Hope that he'd always love her; however, Liam had to hear Hope say she was choosing Thomas instead.

Liam spent his time working, confiding in Bill, and pining for Steffy, though he took no real action to win her. Despite remaining in both Steffy and Hope's orbits, Liam came to realization that he had spent too much time waffling between them and decided to focus on soul searching and self-improvement. Liam met with a visiting Ivy and was surprised when she expressed an interest and kissed him. Liam seemed amused when an apparently jealous Steffy arrived and made catty comments about Ivy's intentions towards him. However, Ivy's return was brief, and Liam went back to offering Steffy support, especially about Finn's continuing compassion toward Sheila.

Liam got a surprise when it turned out Bill had another mystery child in Luna Nozawa, an intern at Forrester Creations. Liam learned the story of how Bill had met Luna's mother, Penelope "Poppy" Nozawa, at a music festival two decades earlier and embraced Luna as his half-sister. Liam shared Steffy's suspicions that Sheila, who was working at Deacon's restaurant, was responsible for the deaths of two of Sheila's fellow employees and commended Finn for telling the police to arrest Sheila.