A patient comes to his senses in a mental hospital. He doesn't remember who he is and how he ended up there. The chief doctor tells him that his name is Ivan and that he was forced to stay in the hospital. When the chief doctor dies, Ivan and his neighbor from the ward Arthur and a police detective Stas Krasivtsev start to investigate his death.
A lawyer Piforskiy and Ivan's wife Nastya whom he can't remember come to the clinic. They assure him that his name is Pavel Alpatov. They help him get discharged. Ivan-Pavel demonstrates brilliant analytical skills. He helps Stas Krasivtsev, the police detective, to solve crimes. Ivan-Pavel wants to find out more about his past with Stas's help.
Ivan-Pavel and his old friend Lekha are trying to find compromising materials against the Stefania pharmaceutical company involved in Ivan's kidnapping. They are being attacked and warned not to continue with the investigation. Ivan-Pavel thinks that Lekha and Nastya are cheating on him. Stas and Ivan investigate the death of a man who was found in a rubbish bin with five bullets in his chest.
Together with Stas, Ivan is trying to find a maniac who strangles girls and leaves their bodies in rubbish bins. To sort out the Stefania case, Ivan-Pavel turns to lawyer Piforskiy; however, the latter doesn't want to start a conflict. Ivan-Pavel falls in love with Nastya and finally comes to believe that she is indeed his wife.
Ivan-Pavel keeps forgetting things; he can't remember what he had been doing just recently, so he decides to continue his treatment. Olga believes that Ivan's state deteriorates and worries for him. Nastya is offended with his suspicions of her unfaithfulness and leaves Ivan-Pavel. Stas Krasivtsev and Ivan-Pavel come to the zoo where a bear was shot down.
Ivan-Pavel decided not to dig into his past and wants to start the life anew instead. He plans to make up with the management of the Stefania. Ivan-Pavel thinks that all his troubles are behind him when Nastya is murdered before his very eyes.
Nastya's death devastates Ivan-Pavel. He wants to revenge on the Stefania and turns to Piforskiy for help again. When he and Stas are on the way to the summer cottage of the Stefania's director, Lekha suddenly disappears. Obsessed with thoughts about Nastya, Ivan-Pavel takes it out on Olga.
Stas now believes Ivan-Pavel and offers him help in investigating the connection of the Stefania with the criminal authority Senya Dikiy. They find dead bodies buried in concrete at the Stefania's construction site and make this fact public. Ivan-Pavel accidentally sees an ad with Nastya and realizes that she is an actress.
Ivan finds Nastya in the airport, kidnaps her and interrogates. He finds out the truth about her and Lekha. He finds out about his fiancé Diana Kulchitsaya and goes to the pharmaceutical plant in Saratov. There, he meets a former colleague who tells him that Ivan disappeared a year ago, and Diana died. Diana's father is looking for Ivan to take vengeance on him for his daughter's death.
Ivan escapes. On coming back home, he tells everything to Stas who starts helping him. Olga turns to her formed classmate Yura Mikheyev who makes experimental procedures with memory. Meanwhile, an investigation about illegal surgeries with donor organs is ongoing.
Thanks to Mikheyev's methods, Ivan remembers his past. He realizes that he used to do bad things. Journalist Goryanskiy comes to Olga in the hospital and makes inquiries about her former patient Ivan Satnov. Olga and Ivan suspect that Goryanskiy was sent by the enemies. Somebody attacks Ivan in his apartment: somebody is watching him and trying to control him.
Ivan tells Stas about the attack and they decide to use Ivan as a bait. Stas follows Goryanskiy who follows Ivan. A famous football player Filimonov gets into a car crash in his Ferrari. Ivan undertakes the investigation of his death.
Goryanskiy investigated professional activities of Ivan Stanov and Diana and found out that they invented a panacea from flu. The only person who may tell about it is pharmacologist Peter Vince who had worked for Ivan and disappeared too. A man is killed in the deposit storage premises while attempting to open a bank cell.
Goryanskiy informs Ivan that he has found pharmacologist Peter Vince. Ivan goes to Goryanskiy to get the information. The main hero starts a relationship with Olga and the situation gets even more complicated. Meanwhile, Stas asks Ivan to investigate another murder. During reconstruction of the Waterloo Battle an IT-specialist, one of the creators of a popular computer game, is shot.
Ivan arranges a meeting with Peter Vince in the airport. Vince gives Ivan a file with information on the revolutionary anti-flu medicine that has a serious side effect - infertility. Journalist Goryanskiy is murdered. Stas finds out that Ivan talked to Goryanskiy before his death.
Ivan kills Deymin, his ex-business partner, and flees the crime scene. Stas finds a record of the surveillance camera capturing Ivan leaving his home with a gun in his hand. Stas destroys the recording, Ivan comes to Olga and she convinces him to stay in the clinics again. However, somebody attempts to kill Ivan in the mental hospital.