1986, Moscow region. A mutilated body of a child is found in the area of government dachas. Three investigators take on a case that will change each of them forever.

The next victim of the maniac becomes a teenager from a local pioneer camp, and the only witness again turns out to be ten-year-old Igor Maltsev.

The main suspect escapes from the investigators, and another child disappears in the area.

Suspect Makurin has been caught, but investigators are waiting for a new terrible find. Meanwhile, Zhenya Bokova is getting worse, and Igor Maltsev's father decides to publish a devastating article about the investigation.

The group detains librarian Dmitry Laval, but they lack direct evidence.

The mystery of Igor Maltsev has been solved, the Fischer case continues to destroy the lives of its leading investigators, and another tragedy occurs at a stable near Moscow.

1992. Three children go to the slot machine club and do not return home. Bokov, Kozyrev and Dobrovolskaya will have to face the Fischer case again.

While Dobrovolskaya and one of the teenagers are imprisoned in Fischer's basement, Bokov and Kozyrev go after the killer.

While Fischer has not yet been sentenced to death, Prosecutor’s Office investigator Yevgeny Bokov tries to get him to talk. They need to find out how many crimes the serial killer actually committed and where to search for one of the boys’ bodies. Meanwhile, somewhere in the mountains of southern Russia a terrible car crash occurs. At the crash site they find a bag stuffed with dollars, and acting police chief Nadezhda Raykina and investigator Zlobin take the case. On the very first day the investigation hits a dead end, and Bokov receives a letter asking for help from a desperate stranger.

After the tragic night, the police organize a search for the missing mother and her older daughter, and seasoned investigator Yevgeny Bokov helps his young colleague cope with the stress. Meanwhile, on the shore of the Black Sea, visitors from Moscow discuss an illegal deal and anticipate pulling off a big score. The resort town becomes unsafe, and the mayor gives Nadezhda Raykina a hard ultimatum — find the criminal within 48 hours.

While Bokov goes it alone using a decoy to catch the criminal, Kozyrev in Moscow takes on Fisher’s interrogation. Meanwhile, another brutal murder occurs in the southern town, but the police still don’t know whether it’s connected to the child abductions. Young investigator Zlobin is home less and less, and a desperate Dina plans to go out without her husband. Kurortnoye has become extremely dangerous, but the residents don’t know it — except for the police, the mayor, and a few parents whose daughters vanished without a trace.

Mayoral candidate debates are approaching, and Valentina Ivanovna demands that the murder suspect be found and put behind bars immediately. Meanwhile Yevgeny Bokov and Vanya Zlobin investigate a new crime at the local apiary, and Nadezhda Raykina learns a terrible secret about her younger sister. Soon the investigators get a solid lead — but what if it’s a false trail?

Yevgeny Bokov suspects a mass killing took place in the mansion, but the mayor presents the tragedy as an accident. During interrogation, Ostrovsky reveals compromising facts from Slava Vdovin’s past, and the fleeing young man is declared wanted. Meanwhile Zlobin finds the ritual shop where the black ribbon was purchased, and the investigation gets a new witness — a surviving victim of the serial killer.

The surviving victim of the maniac regains consciousness, and the investigators have many questions for her. During a search of Zhivoy’s apartment they find circumstantial evidence that expert Varya must carefully examine, and the site of the new murder in the woods is cordoned off until dawn so it can be inspected in daylight. Meanwhile the mayor invites journalists to the hospital to show that Lena Trofimova’s life is not in danger.

After meeting with a psychic, the investigators pick up new leads, and Bokov gets a tip where to find Slava Vdovin. Meanwhile Valery Kozyrev arrives in Kurortnoye and his presence completely changes the situation in town. Nadezhda Raykina continues fighting to adopt Masha Yershova and is preparing for her younger sister’s wedding, which is tomorrow. After a long day at work, Yevgeny Bokov invites Lyuba to a double date at a restaurant with Vanya and his wife.

Tensions in Kurortnoye have reached a boiling point: residents are outraged and demand the town be made safe. Nadezhda Raykina is torn between the investigation, her pregnant younger sister’s wedding, and her feud with the mayor. Forensic expert Varya organizes a search operation, Zlobin continues interrogating Slava Vdovin, and Bokov looks for evidence against the new suspect. Meanwhile in a Moscow prison, the maniac Sergey Golovkin confesses why he killed people.