In the summer of 2017, Anna Devane learned about a woman named Cassandra Pierce, who had worked with Valentin Cassadine during his years as a thief and mercenary. Hoping to prove that Valentin was still engaged in criminal activity, Anna enlisted Dr. Hamilton Finn's help to get close to Cassandra. Finn refused to get involved in Anna's case, but she threatened to charge him with crimes related to when he'd been taking an illegal drug called Zekenestrol to treat his Blackwood's syndrome.

Anna explained that Cassandra was a hypochondriac who would jump at the opportunity to have an infectious disease specialist of Finn's caliber offer to help diagnose what was ailing her. Finn reluctantly accompanied Anna to Monte Carlo, where Cassandra lived. Anna knew that Cassandra was a creature of habit who stopped by a popular café every day, so Anna laid in wait then slipped a harmless drug into Cassandra's coffee that mimicked anaphylactic shock, prompting Finn to spring into action and "save" Cassandra. As anticipated, Cassandra took an interest in Finn when she learned that he was a doctor, and she invited him to her villa.

Finn explained that he couldn't treat Cassandra because he was on vacation with his lover, Anna, and he practiced medicine in the United States, but Cassandra was undeterred. She followed Finn to Port Charles, and he ran a battery of tests on Cassandra to buy Anna time to get what she needed on Cassandra. As Anna had hoped, Cassandra reached out to Valentin, but he was not receptive to helping Cassandra peddle a highly addictive opioid she was close to developing. Valentin informed her that he had retired, but Cassandra forced his hand by threatening his wife and daughter.

To Anna's shock, Valentin offered to help Anna take Cassandra down because he realized that Cassandra would always remain a threat to his family. Finn was equally determined to help Anna because the opioid epidemic in Port Charles had hit close to home due to his own struggle with addiction. Anna refused to endanger Finn any further, but he explained that he was in a perfect position to manipulate Cassandra because she trusted him, she needed a chemist to help her complete the formula for the drug, and Cassandra had made her attraction to Finn very clear.

Anna reluctantly gave Finn a bug to plant in Cassandra's cell phone that Anna had hoped would provide her with the information needed to locate the facility where Cassandra was manufacturing the powerful opioid. Finn successfully planted the bug and gave Cassandra a formula to complete the production of her addictive opioid, knowing that the WSB would seize the drugs before they hit the streets. Things went awry when Cassandra paid Valentin a visit to inform him that she wanted him to accompany her to the facility. Valentin objected because it was New Year's Eve and his one-year wedding anniversary, but Cassandra made it clear that Valentin didn't have a choice. Furious, Valentin plucked her phone out of her hand and threw it across the room.

Cassandra's bodyguard picked up the phone, but he found the listening device. Livid, Cassandra and her henchman abducted Valentin then held him prisoner in a warehouse where she had Erich try to beat a confession out of Valentin. Valentin insisted that he had no idea who had planted the bug, prompting Cassandra to figure out that it had been Finn. Cassandra arranged for Erich to abduct Anna and tie her up at the warehouse with Valentin while Cassandra laid in wait for Finn in Anna's house.

Cassandra confronted Finn about his betrayal then pulled out a cosmetic compact filled with the newly made opioid in powder form. She blew the powder into Finn's face then informed him that she intended to force him to work for her by getting him hooked on the opioid. Finn vowed to fight her, so she pulled out a syringe filled with more opioid and threatened to inject him with an overdose. Finn fought through the effects of the drug and launched himself at Cassandra.

Meanwhile, Anna and Valentin had managed to escape from the warehouse. Anna raced to her house, fearful for Finn, and was stunned when she found Cassandra unconscious on the floor with the syringe sticking out of her chest. Finn stumbled into the room in a drug-induced haze, and Anna rushed to help him.

At the hospital, Finn recovered from his ordeal while Jordan questioned Anna about Cassandra because Cassandra had been found dumped in an alley, barely clinging to life. Anna explained that she had found Cassandra unconscious on the floor, but Cassandra had vanished while Anna had been distracted trying to help Finn. After Jordan left, Anna checked on Finn then paid Cassandra's hospital room a visit. Cassandra lingered in a coma, and her prognosis was grim. Anna contemplated turning off Cassandra's life support to make certain that Cassandra was never a threat to anyone again, but in the end, Anna called the WSB.

Cassandra was taken into custody and transferred to a medical facility. Later that day, Jordan returned to let Anna and Finn know that Cassandra's accomplice had been apprehended, and Erich had confessed to injecting Cassandra with the syringe. According to Erich, he had been horrified when he had realized that Cassandra had intended to murder Anna and Valentin, so he'd gone to Anna's house to inform Cassandra that he was out.

Erich claimed that Cassandra had tried to attack him with the syringe, but he'd managed to overpower her and injected her with the massive dose of opioid. He'd hidden when Anna had arrived home then had waited until Anna was busy with Finn before scooping up Cassandra and leaving. Later, he had left Cassandra's body in an alley. However, Erich had lied.

On January 10, police commissioner Jordan Ashford paid Valentin a visit to question him about his visit with Erich, while Eric had been in lockup. Valentin didn't flinch as he reminded Jordan that he had helped Anna build a case against Cassandra. Jordan knew that Valentin had been behind Erich's confession, but she couldn't prove it. Jordan was right; Valentin had persuaded Erich to confess for a handsome price.

In truth, Valentin's beloved wife, Nina, had been response for Cassandra's coma. Nina had gone to Anna's house looking for Valentin, but instead she had encountered a syringe-wielding Cassandra. Nina had acted in self-defense as she had gained the upper hand and plunged the syringe into Cassandra's chest. Moments later, Valentin had arrived, and it had been Valentin who had moved Cassandra's body to an alley.

In August 2018, Anna was abducted, and Finn turned to Robert Scorpio for help. Robert had a tracking device implanted in Finn because he suspected that Anna had been taken to get to Finn. As Robert had suspected, Finn was abducted. Finn and Anna reunited, but Anna hadn't been ready to be found. Despite being held prisoner, Anna removed the tracking device from Finn's arm because she was determined to uncover the secret that their captors were hiding.

That secret turned out to be Cassandra -- the captors wanted Finn to find a way to wake Cassandra up. Finn balked at helping the woman who had tried to kill him, but the captors were unmoved. Anna interceded, and she convinced Finn to cooperate. Finn read over Cassandra's medical chart then immediately demanded that everyone don a surgical mask for their own protection. After the men left, Finn grabbed some vials and a syringe to create a concoction. After he injected the substance into Cassandra's I.V., she moaned then slowly opened her eyes.

"What happened?" Cassandra weakly asked. Anna quickly explained that they were all being held captive, but Anna had no idea who was in charge. Anna hoped that Cassandra might be able to help, but Cassandra wasn't interested. "Go to hell," Cassandra spat. Finn stepped up to explain that Cassandra had been in a coma for eight months, during that time she had contracted a rare blood disorder. Anna warned Cassandra that her options were limited; Cassandra could help them or Finn could put Cassandra back in a coma.

Cassandra wondered if Valentin had been responsible for their plight, but Anna reiterated that she had no idea who had been behind the abductions. As their captors approached the door, Cassandra agreed to help Anna and Finn. Cassandra closed her eyes to feign being in a coma. Meanwhile, Finn readied several doses of medication to protect everyone from the infectious disease that he claimed had been ailing Cassandra. The leader of the group was leery to accept anything from Finn, so he switched doses with Finn and Anna then handed one to his companion.

Moments later, the armed men crumbled to the floor. Finn had been expecting the switch. Cassandra sat up in bed and looked at the men, but she didn't recognize either. Anna didn't trust Cassandra, so she decided to leave Cassandra locked in the room until they could find help. Shortly after Finn and Anna had slipped out of the hospital room, locked the door, and made their way to an exit, Robert and Finn's brother, Detective Harrison Chase, arrived. Anna led Robert and Chase back to Cassandra's locked hospital room, but Cassandra had vanished.

Meanwhile, Cassandra had found herself a prisoner in the back of a limousine. The man seated next to her remained a mystery except that he wore a signet ring with the Cassadine crest. Alarmed, Cassandra asked what the man wanted from her, but he just patted her hand as if to reassure her.

On July 31, 2019, Cassandra surfaced on Sonny Corinthos' private island in Puerto Ricco. She was startled when she struck up a conversation with two American tourists who turned out to be Michael Corinthos and his girlfriend Sasha Gilmore. Cassandra introduced herself as "Sandy Lance," chatted with the couple for a bit then made plans to join her two new friends for breakfast in the morning. Later, Cassandra called a contact to report that she'd been compromised, and that she needed to be relocated. The following morning, Cassandra was on the phone as she finalized her travel plants and thanked her contact for filling her request. She glanced into her purse where a syringe sat next to a gun.

After the call, "Sandy" waited for the server to finish setting out breakfast. Once he walked away, she injected a halved grapefruit with an unknown substance. Moments later, Michael and Sasha entered the restaurant. "Sandy" made certain that Sasha ate the drugged grapefruit then snapped pictures of the three of them. After breakfast, "Sandy" announced that she was leaving the island, but she hoped to run into Michael and Sasha in the future.

Later, it would be revealed that Cassandra had exposed Nina's daughter to Avian Influenza A, which had nearly cost Sasha her life. Cassandra wanted Valentin and Nina to know that she could get to them at any time. Unfortunately for Cassandra, she had incurred the wrath of Sonny Corinthos for the threat that she had posed to both Michael and Sasha.

On September 13, 2019, Cassandra turned up in Port Charles hiding out on the Haunted Star. Curtis Ashford and Laura Collins had decided to search the ship for a codicil to Mikkos Cassadine's will that Helena had hidden. Cassandra had been forced to reveal herself when the pair had ended up in her state room. Cassandra pulled out a gun then bound the pair as she demanded to know what they had been searching for because she had overheard enough to realize that it had involved Valentin. Cassandra lost the upper hand when Curtis had managed to break loose from the restraints and secure the gun from his captor.

Cassandra was arrested, but she asked to speak privately with Laura when they arrived at the police station. In the interrogation room, Cassandra offered to give Laura what she needed to take Valentin down once and for all in exchange for Cassandra's freedom. Laura declined the offer, prompting Cassandra to reach out to Valentin for assistance by attempting to blackmail him. Cassandra reminded him that she still had Claudette ready to testify against him, but Valentin informed Cassandra that she should have checked because Claudette had flown the coop long ago.

Sonny also stopped by to visit Cassandra. She tried to intimidate him by warning him that mob bosses were not happy with him, but Sonny saw through the desperate attempt at deflection, and he warned Cassandra that she was living on borrowed time. To Cassandra's relief, her partner had arranged for Alexis Davis to represent Cassandra. Cassandra wanted to fight her extradition to the Hague to face trial for her crimes. After Alexis left, Cassandra called her partner to make it clear that she wouldn't hesitate to share what she knew to secure her freedom.