After Ava Jerome suffered devastating facial scars in a fire, Valentin Cassadine put her in touch with the doctor who had, years earlier, transformed him from a series of disfiguring birth defects. Ava traveled to St. Petersburg, Russia, and checked into an upscale private clinic where she met Dr. Richard Klein. Klein agreed to help Ava, but he warned her to stay away from a heavily sedated patient known only as "Patient 6" because the man was dangerous and prone to fits of violence. Ava disregarded the advice and quickly realized that Patient 6 was kept heavily sedated because he was a prisoner.

Ava kept her concerns to herself because she was desperate to have her scars repaired, but Klein kept finding Ava with Patient 6. Klein warned her that he would not treat her if she continued to defy his orders, so Ava turned over a piece of paper with a phone number scribbled on it that Patient 6 had given her. Dr. Klein took the number and contacted a mystery person to warn the person that Patient 6 could no longer be controlled with the powerful tranquilizer they'd been giving him. The mystery person instructed Klein to increase the dosage, despite the danger of an overdose.

Klein followed orders, but Patient 6 managed to fight off the effects of the drug and, with Ava's help, escape the clinic. Klein was furious and sent his henchmen after Patient 6. He also refused to continue to treat Ava, despite the success of the first treatment. Klein locked Ava in her room, but she managed to escape and returned home. Klein was not far behind her because his men had tracked Patient 6 to Port Charles.

Klein was desperate to apprehend Patient 6 because he knew that Patient 6 was really Jason Morgan. Klein turned to Andre Maddox for help. It was revealed that Klein and Andre answered to the same mystery man. Andre had been instrumental in mapping the memories of both Jason Morgan and Jason's long-lost identical twin, Andrew Cain, and implanting Jason's memories into Drew. Andre had been sent to Port Charles a couple of years earlier to monitor Drew and to make certain that Drew's original memories remained buried. Andre explained that Franco Baldwin had been asking questions about Drew because Drew had been raised as Franco's brother for the first few years of Drew's life.

Klein provided Andre with a falsified death certificate for "Andrew Moore" in the hopes that it would put an end to Franco's search. Meanwhile, Klein ordered his henchmen to go to Metro Court, where Sam and Jason/Drew were hosting a launch party for their new media company. Klein hoped to use Sam to draw out the real Jason Morgan/Patient 6. The plan worked, but things quickly fell apart when Patient 6/Jason chased the henchman, who had drugged and kidnapped Sam, to the pier where Klein was waiting. Klein panicked when Jason shot the henchman, so Klein tossed an unconscious Sam into the frigid harbor water then fled.

Klein reached out to Valentin Cassadine for help, but Valentin refused to lift a finger. Valentin called the police and told them where to find Klein. Klein was arrested, but Sonny Corinthos bailed him out of jail because Sonny wanted to know who Klein's boss was. By that time, Andre had been arrested for his crimes, and he confessed the truth about Jason and Drew's abductions and the memory-mapping experiment that had left Drew with only Jason's memories. Jason and Sonny demanded to know who Klein had been answering to, but Klein admitted that he didn't know the man's identity because they had only communicated by phone.

Klein agreed to help Jason and Sonny draw the man out of hiding, but Klein wanted help to disappear because he feared that his boss would retaliate. The mystery man called Klein, and Sonny's tech guy, Brick, was able to trace the call to Port Charles, but not to the exact location, and he was unable to learn the name of the caller. Sonny agreed to let Klein leave but nothing more. Grateful, Klein left Sonny's office and vanished.