Friends and relatives came to Robert and Fred Kaplen in Chantbary Cloe for lunch. Among the invited are the married couple Gordon and Betty Whitehouse, an employee of the publishing house Oluen Peale, one of the newly appointed directors of this English publishing house Charles Trevor Stanton, and, finally, the writer Maud Mokridge. While the men are talking in the dining room after lunch, the women, returning to the living room, decide to listen to the play on the radio, which they began to listen to before dinner. During lunch, they skipped five scenes of this play and now do not quite understand why it is called “Sleeping Dog” and why in the finale a deadly pistol shot is heard. Oluen Peel suggests that the sleeping dog personifies the truth that one of the characters in the play wanted to know. Having woken up the dog, he learned the truth and the lie so plentiful in this play, and then shot himself. Miss Mockridge, in connection with the suicide in the play, recalls Robert's brother, Martin Kaplen, who shot himself dead a year ago in his cottage. The men who returned to the drawing room ask questions about the content of the heard play and discuss how much it is advisable to speak or hide the truth. Their opinions differ: Robert Kaplen is sure that it is necessary that sooner or later everything comes out. It seems to Stanton that telling the truth is like making a dangerous turn at high speed. The hostess of the house Fred is trying to translate the conversation on another topic and offers guests drinks and cigarettes. Cigarettes lie in a box that Oluen seems familiar with - she already saw this beautiful thing from Martin Kaplen. Freda claims that this is not possible, since Martin got it after Oluen and Martin saw each other for the last time, that is, a week before Martin’s death. Oluen, shy, doesn't argue with Freda. This seems to Robert suspicious, and he begins to question. It turns out that Freda bought this music box-cigarette box Martina after their last joint visit to him and brought it on that fateful day. But after her in the evening, Oluen also came to Martin to talk with him about a very important matter. However, neither one nor the other has so far said anything to anyone; they have concealed their last visit to Martin from the investigation. Discouraged, Robert says that now he is simply obliged to find out the whole story with Martin to the end. Seeing Robert's serious zeal, Betty begins to get nervous and insistently persuades her husband to go home, citing a severe headache. Stanton leaves with them.

Left three (Mod Mokridge left even earlier), Robert, Fred and Oluen continue to remember everything they saw and experienced. Oluen admits that she went to Martin because she had to find out the question that tormented her: who nevertheless stole the check for five hundred pounds - Martin or Robert. Now, however, everyone says that Martin did this and that, apparently, this act was the main reason for his suicide. But Oluen is still tormented by doubts, and she directly asks Robert if he took the money. Robert is outraged by such suspicions, especially because they are expressed by a person whom he always considered one of his best friends. Here Fred, unable to stand it, tells Robert that he is a blind man, if he still does not understand that Oluen has love for him, and not friendly feelings. Oluen is forced to admit this, as well as the fact that, while continuing to love Robert, she actually covered him. She didn’t tell anyone that Martin convinced her that evening of Robert’s dishonest act and that his confidence was based on Stanton’s testimony. A stunned Robert admits that Stanton also pointed to him as a thief and said that he did not want to extradite Martin, because the three of them are jointly responsible. Fred and Robert conclude that, therefore, Stanton himself took the money, since only Robert, Martin and Stanton knew about them. Robert calls the Gordons, who still have Stanton, and asks them to come back to find out everything, to shed light on all the secrets.

Men return alone - Betty stayed home. A flurry of questions falls upon Stanton, under the pressure of which he admits that he really took the money, in dire need of it and hoping to cover the shortage in a few weeks. It was on one of these alarming days that Martin shot himself, and everyone thought that he had done this without surviving the shame of the theft and being afraid of being exposed. Then Stanton decided to keep quiet and not admit anything. Fred and Gordon do not hide the joy of learning that Martin has kept his honest name, and pounce on Stanton with accusations. Stanton quickly pulls himself together and recalls that since Martin's life was far from righteous, the latter should have had some other reason for suicide. Stanton no longer cares, and he says everything he knows. But he knows, for example, that Freda was Martin's mistress. Freda is also determined at this moment to be frank, and she admits that she could not break the love affair with Martin, marrying Robert. But since Martin did not really love her, she did not dare to break up with Robert.

Gordon, who idolized Martin, pounced reproachfully on Olouen, who had just admitted that she hated Martin for his treachery and intrigue. Oluen admits that it was she who shot Martin, but not intentionally, but by accident. Oluen tells that she found Martin on that fateful evening alone. He was in a terrible state, drugged by some kind of drug and suspiciously funny. He began to tease Oluen, called her a prim old maid, rooted in prejudice, said that she never lived a full life, said that she in vain suppresses the desire that she has for him. Martin became more and more excited and suggested that Olouin take off her dress. When the indignant girl wanted to leave, Martin blocked the door, and in his hands appeared a revolver. Oluen tried to push him away, but he began to tear off her dress. Defending herself, Oluen grabbed his hand, in which there was a gun, and turned the gun with the barrel to him. Finger Olouen pulled the trigger, a shot rang out and Martin fell, hit by a bullet.

All those present are shocked by what they heard and at the same time confident in Olouin's innocence. They decide to keep this secret in the future. Stanton alone does not seem to be very surprised. He had long suspected this, for he had discovered a piece of cloth from Olouin’s dress in Martin’s cottage. Stanton was always respectful of Olouin and was confident in her moral purity. Continuing her confession, Oluen says that when she came to her senses a bit, she wanted to share what happened with someone and went to Stanton's cottage. Approaching the house, she saw two there: Stanton and Betty, and, of course, turned back. These words make a depressing impression on Robert, who directly asks Betty, who nevertheless then came here if she was Stanton's mistress. He receives an affirmative answer and Betty’s recognition that her marriage to Gordon was a complete pretense that nothing but shame and humiliation, this marriage did not give her. She admits that she and Stanton did not come out of great love, but because Gordon’s behavior drove her crazy, and because Stanton gave her expensive gifts. Robert confesses for the first time that he idolized Betty, but the young woman tells him that he adored not her, but only her beautiful image, youth, which is not the same thing. Robert and Gordon, each in their own way, reiterate their anger at Stanton, claiming that they no longer want to have anything to do with him: he should leave immediately and not forget to submit his resignation letter, as well as return five hundred pounds. Robert leans on whiskey and admits that everything from now on in his life will be meaningless and empty. Having lost Betty, he lost his last illusion, and without illusions he cannot live - it was in them that he drew hope and courage. Today, his whole world has collapsed through his fault, and the future for him no longer exists. In despair, he leaves. Freda recalls that Robert has a revolver in his bedroom. Oluen is trying to stop Robert ...

In a gradually approaching darkness, a shot is heard, then a woman's scream and sobs are heard, just like at the beginning of the play. Then gradually the light is again lit, illuminating all four women. They discuss the play Sleeping Dog, broadcast on the radio, and the laughter of men comes from the dining room. When men join women, a conversation begins between them, like two drops of water similar to the conversation at the beginning of the play. They discuss the name of the play, Fred offers guests cigarettes from the box, Gordon is looking for dance music on the radio. The motive of the song “Everything could have been different” is heard. Olouen and Robert dance the foxtrot to the sounds of louder and louder music. Everyone is very cheerful. The curtain slowly lowers.