Act I
Act I opens at Andrew Wyke's country house. The acclaimed mystery writer is working on his most recent novel, when the doorbell rings. At the door is Milo Tindle. Andrew has invited the younger man over to discuss Andrew's wife. Marguerite.

Milo wants to marry her. Andrew does not think that Milo will be able to keep Marguerite in the lavish style to which she has grown accustomed. However, Andrew has a mistress himself, and he is more than happy to have Marguerite taken off his hands. He proposes a plan, which he has already worked out: Milo will "steal" some jewels that Andrew owns and sell them abroad. Thus Milo will have the money needed to support Marguerite; Andrew will be done with his lavish wife and, at the same time, get a hefty settlement from his insurance agency.

Milo is initially suspicious. He is afraid of getting caught, and he is also afraid that Andrew will actually try to frame him for the theft. However, the lure of the money is too great for Miio, and he agrees to the plan.

Andrew has determined that Milo must actually "break in" to the house to make the theft look real. He also wants Milo to wear a disguise. After the two men go through a hamper filled with costumes, Mito ends up dressed as a clown.

Milo goes outside to the shed, where Andrew has left a ladder. He uses the ladder to enter the upstairs gallery through the window. Milo wants to go straight for the safe, but Andrew insists that he ransack the house a bit, to make it look like he is looking for the jewels. Then Andrew takes Milo to the safe, explodes it, and hands Milo a jewel box. Andrew declares that, to make the burglary seem more real, they must enact a scene in which he, Andrew, surprises the burglar, and the two men struggle. He will then be able to give the police a false description of the intruder. The two men begin to toss things around the room and wrestle a bit. Out of his desk drawer, Andrew pulls a gun, which Milo can use to keep Andrew at bay. Andrew shoots several of the items around the room and then points the gun at Milo, while tying him up. Still holding the gun, Andrew declares that he is going to kill Milo He agrees that they have been playing a game all evening, a game in which he kills Milo, and no one suspects him. He tells Milo that he invited him over to create a foolproof murder scene. Milo tries to talk Andrew out of the plan. Andrew resists Milo's plea and pulls the trigger Milo falls down the stairs and lies still.

Act 2
Act 2 takes place two days later. Andrew is at home when the doorbell rings. He lets in Inspector Doppler of the Constable's office. Doppler is investigating the disappearance of Milo Tindle. Andrew claims to have met Milo a few months ago, but Doppler tells him that Milo had reported that he was coming to see him, Andrew, two nights ago. He also tells Andrew that an eyewitness who was passing the house two nights ago claims to have seen a struggle taking place and to have heard three shots fired from a gun. Doppler then went to Milo's house, where he found the note that Andrew had sent him
Realizing he is trapped, Andrew explains that he and Milo were playing a game called Burglary. He tells Doppler that Milo left about 9:30 that evening, and he hasn't seen him since. He says he only wanted to teach Milo a lesson. The story he tells Doppler is as it was portrayed in act 1. He then adds the information that he shot Milo with a blank bullet. Milo was so scared, however, diat he fainted. He regained consciousness a few minutes later and went home.

Doppler does not believe Andrew's explanation and looks around He discovers bullet holes m the wall. At the spot where Andrew claims he shot Milo with the blank, Doppler discovers blood. Doppler looks out the wmdow and asks about the mound of earth in the garden, which Andrew had not seen until then Doppler says they will dig up the garden, and, most likely, find Milo's body. He looks in the wardrobe and finds a jacket of Milo's, though Andrew claims that Milo changed back into his own clothes before he left.

Doppler proposes that the third bullet was, in fact, a live bullet. When Andrew discovered that he had killed Milo, he panicked and buried him in the garden. He will now take Milo down to the station. After Andrew is properly horrified at his impending fate of prison, Doppler reveals his true identity: he is Milo.

Milo wanted to get back at Andrew for scaring him. He had snuck into the house the day before to set the "crime" scene. Andrew says he hoped that Milo was not angry a few days before, that he just wanted to see if Milo was a "game-playing sort of person." Milo says he was not playing a game, he just wanted revenge. However, he then thinks his revenge was not great enough, for he was terrified with death, while Andrew was only teased with prison. Milo, however, wanting to draw level with Andrew in the "game," tells Andrew that he killed Andrew's girlfriend, Tea. Milo says that Tea stopped by the day before, surprising Milo. They had sex, and then Milo killed her. It is her body buried in the garden.

Now Andrew must play another game—the game of finding the clues that Milo planted that will frame Andrew for the murder. He must do so in the next ten minutes, for Milo has already called the police. In a panic, Andrew calls Tea's house but finds that she is missing. Following Milo's clues, he looks for the evidence against him. He finds a bracelet he gave Tea and one of her shoes When the doorbell rings, the police having arrived, Andrew is still searching for the murder weapon. Milo goes to answer it as Andrew discovers, in the grandfather clock, the golden cord used to strangle Tea. Andrew hears Milo speaking with two police officers, but, once again, it is a ruse. Milo is merely mimicking their voices. There are no police officers at all.

Milo returns to Andrew. He tells him that Tea came by and agreed to play a part in the game. Milo goes to get Marguerite's fur coat. Andrew asks Milo to stay with him They are evenly matched game players, and he just wants someone to play with. Milo refuses Andrew feels humiliated until he comes up with another plan. He pulls his gun out of the desk, explaining aloud what happened to an imaginary police inspector. He surprised a man with his wife's fur coat and shot him dead. When Milo returns, he tells Andrew that the game won't work.

He went to the police station and told them what happened on Friday. He realized that the police were not going to do anything, which is when he decided to take his own revenge. Andrew does not believe Milo He says he is going to shoot Milo, this time with real bullets. As Milo starts to leave, Andrew fatally shoots him. As Milo dies, a police car pulls up the driveway. An insistent knocking on the door is heard as the curtain falls.