Marinov, a man with a dark past and a dubious moral, is found dead. Who has done it? Baev whom the neighbors have seen going out of Marinov's flat, Dimov, who is implicated by certain documents, or Zhana, who has probably been the victim's lover? The film expands the traditional format of crime thriller. This is achieved mainly through the character of the Inspector to whom the case has been assigned. His profession brings him regularly in touch with the shady side of life, which the filmmakers have chosen to call 'the night': murders, corpses, post-mortem, deceit, confidence tricks, lies and blackmails. The Inspector, who remembers poignantly a failed love affair, has deliberately chosen a job, which has made him some thing of a hermit. His loneliness, however, does not preclude human contacts in which he is revealed as a fine and delicate person. His attitude to Zhana is a blend of professional duty and human sympathy. He helps her straighten out her life. In the end the Inspector proves that Marinov has committed suicide but more importantly, he proves that man can always be won over to the cause of a higher morality.