Professor Chekulaev’s wife, Anna, was brutally murdered. At her neighbor Pavlov's place, detectives found the murder weapon - a hammer with traces of the victim's blood. The case was closed, Pavlov received a sentence. But the convict’s friend, newspaper editor Gennady Nekhvatov, cannot come to terms with this. He has irrefutable evidence of Pavlov’s innocence, which he is going to make public with the help of the famous journalist Aristarkh Rusakov. The meeting is scheduled at the bus stop. Having agreed with Nekhvatov on further actions, Rusakov is about to leave, when he suddenly notices a suspicious old woman with a “diplomat” exactly like Nekhvatov’s. The old woman's sly gaze seemed very familiar to Rusakov...