After news of the future birth of a child, Sergei split from his wife, Natasha, and settled in the company of young architects, who occupied a room in a big house. As a result of a chain of unforeseen events, brought by one of the tenants found a child, Sergei finds a newborn son. Friends are doing everything possible to find a lost mother, but Sergei does not disclose their affiliation and tries to give the baby the wrong hands.

A first part of story about a Soviet spies trying to infiltrate German Intelligence center "Saturn" during and after the WWII.

A police detective is trying to find a murderer who uses a new recently developed drug for his crimes.

KGB agents are organizing the disinformation campaign for a western spy.

After Tulyev's arrest, Soviet counterintelligence continues the radio game with the enemy, sending encryptions signed "Nadezhda" to the Western intelligence center. KGB officer Sinitsyn, friendly towards Tulyev, tries to persuade him to take his side — he arranges a meeting to a scout with Mariya and her son, whom he has never seen before. In addition, Mikhail learns that his father didn't die of his own death, but was most likely killed. Meanwhile, a young Soviet scientist Borkov, who spoke at an international conference about his innovative work, finds himself in the spotlight of the Western security services.