On the morning of November 3, 1948, Alfons Klenen, a policeman from Twann, bumped into a blue Mercedes, standing on the side of the road in the direction of Aambuen. In the car, he discovers the corpse of a man killed the night before by a shot in the temple from a revolver of a lieutenant of the police in Bern, Ulrich Schmid. He delivers the victim to the police department, where he worked.
The investigation is entrusted to the elderly commissar Berlach, who takes as his assistants a certain Tshants, an employee of the same department. Before, Berlach lived abroad for a long time, was one of the leading forensic scientists in Constantinople, and then in Germany, but back in 1933 he returned to his homeland.
First of all, Berlach orders to keep the murder story a secret, despite the disagreement of his boss Lutz. That same morning, he sets off for Schmid's apartment. There he discovers the folder of the murdered woman with documents, but so far does not tell anyone about her. When the next morning, the Trzantz summoned by him comes to his office, Berlakh for a moment thinks that he sees the late Schmid in front of him, since the Trzantz is dressed exactly like Schmid. Berlach tells his assistant that he realizes who the killer is, but refuses to reveal his name to Trzanc. Trshants himself must find a clue.
From Frau Schönler, in whom Schmid was renting a room, Tshants learns that on the days marked on the calendar with the letter “G”, in the evenings her tenant put on a tailcoat and left home. Trzanz and Berlach are sent to the crime scene. Trzanz stops the car before turning onto the road from Tvann to Lambuen and turns off the headlights. He hopes that where Schmid was on Wednesday, and today a reception is arranged, and expects to go after the cars that will be sent to this reception. This is what happens.
Both police go out near the house of a certain Gastman, a wealthy, surrounded by the honor of a city dweller. They decide to go around the house from different sides and for this they are separated. At the very place where Berlach should already meet with his colleague, he is attacked by a huge dog. However, Tshants arriving in time saves Berlach’s life by shooting an animal. The sound of a shot makes Gastman's guests, listening at that time to Bach performed by a famous pianist, snuggle up to the windows. They are outraged by the behavior of strangers. A national adviser, Colonel von Shandy, who is also Gastman’s lawyer, comes out of the house to talk with them. He is surprised that the police associate his client with the assassination of Schmid, and assures that he never met a person with that name, but asks to give him a photograph of the murdered man. He promises that the next day he will call in the police department of Bern.
Tshanc goes to get information about Gastman from the local police. Berlach, whose stomach aches all the time, goes to the nearest restaurant. Having talked with colleagues, Tshants goes towards Berlach, but does not find the commissioner in the restaurant, gets in the car and drives off. At the place where the crime occurred, a man’s shadow separates from the rock and waves his hand, asking him to stop the car. Trzanz involuntarily slows down, but already the next instant he is struck by horror: after all, probably the same thing happened with Schmid on the night of his murder. In the approaching figure, he recognizes Berlach, but his excitement from this does not pass. Both look each other in the eye, then Berlach gets into the car and asks to go further.
At home, Berlach, left alone, takes out a revolver from his pocket, although before that he told Tshants that he was not carrying weapons, and, having removed his coat, unwound several layers of fabric with which his hand was wrapped - this is usually done when training service dogs. The next morning, Lutz, chief of Berlach, is visited by Gastmann's lawyer, Colonel von Shandy. He intimidates Lutz, who owes the colonel his promotion. He tells Lutz that Schmid was most likely a spy, as he appeared in the evenings under an assumed name. He argues that it is impossible to associate the murder with the name of Gastman, as this threatens with an international scandal, because at the Gastman evenings, large industrialists of Switzerland meet with diplomats of high flight of a certain power and conduct business negotiations there, which should not be made public. Lutz agrees to leave his client alone.
Having returned from Schmid’s funeral, Berlach finds in his house a sheet of Schmid’s folder, a calm, closed man with deeply sunken eyes on his broad, cheeky face. Berlach recognizes in him his old acquaintance, who now lives under the name of Gastman. Forty years ago they bet in Turkey. Gastman promised that in the presence of Berlach he would commit a crime, and he would not be able to convict him. Three days later, it happened. Gastman threw the man off the bridge, and then gave his death as suicide. Berlach could not prove his guilt. Their contest has been going on for forty years and, despite Berlach’s forensic talent, each time ends not in his favor. Before leaving, Gastman takes Schmid’s folder with him, which, as it turns out, was sent by Berlach to follow Gastman. This folder contains documents that compromise Gastman, without which the commissioner again turns out to be powerless against his opponent. Before leaving, he asks Berlach not to get involved in this matter.
After the guest leaves, a stomach attack occurs with Berlach, but he still soon goes to the office, and from there, together with Tshanets, to the writer, one of Gastman's acquaintances. Berlach builds a conversation with the writer so that Trzantz lost his temper. With his whole appearance, Trzantz shows that he is sure of Gastman’s fault, but Berlach does not react to his statements. On the way back, the conversation between the two policemen comes to Schmid. Berlach has to listen to the full indignation of the attacks of Tshanets against Schmid, who bypassed him in everything. Now Tshantsu absolutely needs to find a killer, because, in his opinion, this is his only chance to attract the attention of his superiors. He persuades Berlach to persuade Lutz to allow him to meet with Gastman. The commissioner, however, assures that he can do nothing, for Lutz is not determined to interfere with Gastman in the murder case.
After the trip, Berlach goes to his doctor, who informs him that no later than three days later he needs to undergo surgery.
On the same night, someone in brown gloves, breaking into the house of Berlach, tries to kill him, but he fails to do this, and the offender is hiding. After half an hour, Berlach calls Trshanza to himself. He tells him that for several days he leaves for treatment in the mountains.
In the morning, a taxi stops near his porch. When the car drives off, Berlach discovers that he is not alone. Nearby sits Gastman in brown gloves. He again demands that Berlach terminate the investigation. He, however, replies that this time he is going to prove Gastman’s guilt in a crime that he did not commit, and that in the evening the executioner will come to him from Gastman.
In the evening, Tshants appears on the estate to Gastman and kills the master along with his two servants. Lutz is even glad that now he will not have to interfere in diplomatic squabbles. He is sure that Gastman was the murderer of Schmid, and Tshantsa intends to upgrade.
Berlach invites Trzantz to his dinner and informs him that Trzantz is the true killer of Schmid. He forces him to confess this. The bullets found near the killed Schmid and in the dog's body are identical. Tshants knew that Schmid was engaged in Gastman, but did not know for what reason. He even found a folder with documents and decided to take up the matter himself, and kill Schmid so that success would go to him alone. It was he who wanted to kill Berlach and steal the folder at night, but he did not know that in the morning Gastman had taken her. Tshants thought that it would not be difficult for him to convict Gastman of the murder of Schmid, and he was right. And now he got everything he wanted: the success of Schmid, his position, his car (Tshants acquired it by installments) and even his girlfriend. Berlach promises that he will not extradite him to the police, provided that Trzanc disappears forever from his field of vision.
That night, Trzantz crashes in his car. But Berlach goes for an operation, after which he has only one year left to live.
