Petra worked with Dr. Meisner to develop the Cicada program, a behavior-modification regimen that brainwashed candidates into forgetting their past and assuming a cover life, complete with ingrained, reflexive loyalty in order to carry out covert missions when instructed. CIA operatives John Randolph Bentley and Frank Ferguson discovered her activities in Krakow and fled, but Petra managed to capture Bentley.
Bentley himself was then placed in the Cicada program by Petra, who found something special about Bentley. She acted as his lover, his "advocate"; a good cop who took his pain away and brought him food and towels in between torture sessions carried out by Meisner's men. Over time the long months of torture began to affect Bentley's mind, and Meisner himself recommended Bentley for termination due to his stubbornness, but Petra eventually managed to get him to confide in her in a moment of weakness. This was confirmation enough for Meisner to begin the drug intake, the next stage in becoming a Cicada.
Under the influence of Meisner's drugs, Bentley began to forget his past and Petra began to train him martially and psychologically. He became a successful fighter, even as he was trained to respond to psychological triggers such as the song Frère Jacques. Petra and Bentley's relationship deepened in this time as well, with Petra no longer simply manipulating him but coming to genuinely care for him.
With Bentley's rapid progress, Petra had him moved to an inn in Budapest owned by Karoli. There she had Bentley torture random criminals in order to become an accomplished interrogator, and she even had him call the CIA for help so that the KGB could ambush and capture one of his former comrades, Don Matheson, to torture. Petra then had Bentley taken to Berlin for his final test; to kill three of his former comrades.
However, Bentley began to balk at the prospect as some of his own memories resurfaced. Petra insisted that his unease and lack of self control was because of their relationship, but Bentley suspected that it was the training, and began to fight against his conditioning, refusing to kill his comrades. Petra then had him sedated and Meisner administered more drugs to Bentley to reinforce the conditioning.
Dr. Meisner thought that Bentley needed more training to be a true Cicada. Petra was insistent that he was ready however, and after calming Bentley, used the song Frère Jacques to activate him. Bentley's reflexes took over, and he unflinchingly murdered his three comrades in rapid succession. Petra took this as confirmation of his training being complete, and prepared to have him sent into the field. Unfortunately for Petra, Bentley finally snapped out of it shortly afterward, stabbed Meisner in the neck, and went rogue. Petra herself fought with Bentley and attempted to prevent him from fleeing, but Bentley managed to slice off her pinky finger and escape.
Undaunted by the injury, Petra gave chase with a strike team to the American safe house he was headed to. Although she arrived shortly after he did, he hid under the stairs while they entered the safe house and, finding nothing, Petra came back out of the building to discover that Bentley had stolen one of their cars and made good his escape.
Petra went into hiding as a farmer's wife in Kursk, Russia. Their house was built nearby the entrance to the secret Stiletto Six, an old Russian nuclear missile that Petra was set to guard. She grew old with her husband Oleg Popov, until one day he bought a new hearing aid after selling their best bull. Petra was disgusted, but Popov was overjoyed at finally being able to hear again, until eventually he began to hear a metallic noise. Petra then took his hearing aid away for his own safety.
Still curious, Popov took the hearing aid back while Petra slept. Petra followed him as he followed the noise to their barn, where he discovered a hidden entrance leading into the earth. He descended, as did Petra, and he passed into a chamber with loud machinery. There, he turned and realized that Petra was standing right behind him. Jubilant, he excitedly told her that he had heard something, but Petra simply stared at him and did not respond. Eventually Popov noticed the sickle in her hand and realized something was wrong, at which point she stabbed him, saying "I tried to warn you". Popov then bled to death at Petra's feet.
Publicly berated by her superior, Yuri, for allowing Bentley to escape, Petra weathered the rebuke in silence until they could have sex in private. They were lovers, and only went through the motions of punishment for public appearances. Petra assured Yuri that she would capture Bentley, expecting him to kill her if she failed.
Back in the present, Petra sought to call her superiors to report her husband Oleg Popov's death by her hand and the discovery of Stiletto Six. Unfortunately, her secure line had been replaced with a clothing store's, so she went to Moscow to report in person, setting up a meeting with Max Schneider and Yuri Leniov.
Still in the present, Petra arrived at her old safe house in Moscow to find the power out, and while in the process of fixing it another resident offered her a fuse. Petra invited the woman into her safe house with an invitation of tea, and while she was distracted Petra assaulted the woman. It appears the woman was an assassin, because she fought professionally, but Petra managed to stab her to death. Enraged, Petra snuck up on Schneider, and demanded to know why he sent an assassin after her while holding a knife to his throat. After learning that Yuri was the one who sent the assassin and that he was in Greece, Petra slit Schneider's wrist, killing him.
Back in 1973, Petra returned to the old inn in Budapest where she had previously trained Bentley. There she discovered that Bentley had visited and that the innkeeper, Karoli, revealed some of their activities to him. She had Karoli killed, and although her subordinate questioned whether she was loyal to the KGB or to Bentley, Petra simply threatened him with murder as well before going out to search for Bentley herself. She found him outside a drug den, tripping on LSD, and promptly ran him over with her car and captured him.
Petra brought Bentley to a construction warehouse and stood over him with a gun until he awoke. When he did, he claimed to have remembered everything, including his torment at her hands. He urged her to kill him, but Petra brought up their relationship, which Bentley promptly wrote off as manipulation. Petra claimed that it was only manipulation at first, her blossoming love for him eventually causing her to doubt Meisner and the program, but Bentley angrily wrote that off as well. It wasn't until Petra shot her own comrade right in front of Bentley that he began to entertain her sincerity.
Bentley demanded to know if Matheson was still alive, which Petra reluctantly confirmed, but when Bentley announced his intention to save Matheson Petra countered that they should simply run away together. Still supremely skeptical however, Bentley wanted nothing to do with Petra, and only by offering to help Bentley save his comrades did she get Bentley to stomach her presence. The two then fought their way out of the warehouse together.
The pair went to a theater where a KGB safe house was present, and once inside Bentley immediately proceeded to grill Petra on where Meisner's new lab was and how many subjects were still alive. Petra didn't know the location, but did know that 3-4 of them were still alive. Despite her cooperation, Bentley couldn't stand to be near her as they were on "different sides", and although Petra insisted that she gave up all sides for him, Bentley insisted on going for a walk alone to clear his head.
He returned shortly afterward, after having just killed Wilson. Fearing that the Americans would never take him back after that betrayal, Bentley prepared to shoot himself. Although Petra tried to comfort him, Bentley pushed her away and nearly shot himself in the head until Petra revealed that Meisner was still alive; Bentley didn't succeed in killing him in The Cicada Protocol.
Although Bentley disbelieved her, she assured him that she could find Meisner's new location via Yuri. Only after promising that she'd help him find his comrades did he let her take the gun from his hands, but he was still enraged. As Bentley grappled with his intense emotion, Petra hopefully stood before him until he gave in and kissed her, leading to them having sex.
In the present, Petra went from Moscow to Mykonos, Greece, where Yuri Leniov was "yachting" on his $300 million personal cruise ship, Ambitisya, Ambition. Petra learned of Yuri's indulgences and abandonment of duty in favor of wealth, which disgusted her as a former KGB operative. She followed to him to his massive villa, and cornered him in his room. She demanded to know what he intended to do with Stiletto Six, and although he revealed that North Koreans were purchasing it and she called him a traitor for it, Yuri countered that her assignment on her farm was really a punishment for her past deeds.
Petra began to break down, shamed by Yuri's devaluation of her entire life of devotion to duty. Yuri called in his guards and revealed to her that he knew she was stalking him, and even had photos of her sneaking about, indicating how useless her training was. WHen she asked if he would kill her, he denied her even that, saying that she'd view it as a noble sacrifice true to the end. He then sent her away, emotionally crushed.
Tara Coleman managed to track down Petra in her old age, and visited her on her farm where she had returned to. Petra let Tara inside her home, but kept her gun concealed and ready.
The morning after, Petra and Bentley prepared to visit Yuri in order to learn where Dr. Meisner's new lab was. Petra insisted that Bentley's performance must be flawless, and then lamented how she'd never be allowed to return to Russia (or Lake Baikal) again. Bentley offered to bring her with him back to Hocking Hills, Ohio, and she accepted his offer.
Bentley then returns her watch to her, and they departed for the meeting with Yuri. At the meeting, Petra pretended to return Yuri's affections and demonstrated Bentley's "loyalty". Yuri wanted to have sex with her right in front of Bentley, but she convinced him to send Bentley away to Dr. Meisner's lab in Romania before doing so.
While speaking with Tara Coleman, Petra pulled a gun on her and Tara eventually revealed that she desperately wanted to find Stiletto Six. Even though she killed her own husband when he found Stiletto Six, after Yuri crushed her loyalty and took the nuclear payload while she was gone, Petra had no reason to hide it anymore. She brought Tara to the warhead and revealed it to her, and the fact that the nuclear payload had been removed.
Saying that Yuri "won", Petra was markedly calm despite the warhead she had been guarding for decades having suddenly vanished. She insisted that it was missing for decades before, and it's still missing now. Eventually Tara received a message on her phone which played Frère Jacques, the very same song Petra instilled into Bentley years ago as a psychological trigger. It immediately activated Tara, who Petra recognized as a Cicada.
Petra returned from her meeting with Yuri to her and Bentley's safe house in Budapest, where she was promptly apprehended by a swarm of CIA agents. She was then brought before Dennis Kohler, who claimed that Bentley betrayed her and that with her own country after her, she has no friends left. He demands everything she knows regarding the Cicada program, but Petra insisted that she'd only speak with Bentley.
Bentley later arrived at her cell, now decorated by the CIA as a hero, and Petra accused him of betraying her. Bentley justified himself by mentioning the other Cicadas she tricked into falling in love with her, but Petra gave up everything for Bentley, and assaulted him in a rage. When Bentley left however, he found that Petra had snuck him a note: "Remember Hocking Hills".
Tara announced her intentions to kill Yuri Leniov, so Petra supplied her with guns and advice on how Yuri fights. Although Tara invited Petra to help fight Yuri, she declined in favor of some "unfinished business". This turned out to be a visit to Bentley, who was still alive after the events of 1973.