Vladimir Ladygin recognizes his former classmate at the medical institute, Kolesov, as a sleepwalker wandering the streets at night, having lost his memory, speech and reason. Having practically pulled him out from under the wheels of a random car and sent him to the clinic, Vladimir begins to investigate the circumstances that led his old acquaintance to such a state. It turns out that Kolesov ran a mysterious secret laboratory. His assistant Katya, a very attractive person, shows Ladygin obvious signs of attention, but Vladimir’s intuition tells him that something is fishy here. And not in vain - during a visit to a secret laboratory, Ladygin is attacked from behind and given a sleeping injection in the shoulder...