The Mousetrap by Agatha Christie was originally performed in London’s West End in 1952. It is a two-act murder mystery play with a twist ending that subverts the traditional genre expectations of detective fiction, set in the early 1950s. The Mousetrap is the longest running West End play, with over 27,000 performances. There have been a few TV and movie versions made in locations such as Germany, the USSR, and India.

This study guide cites the 1982 edition published by Samuel French Inc.

Plot Summary

The Mousetrap begins in darkness, with only the music of “Three Blind Mice” playing. This is followed by the sounds of a crime and a radio reporting on a murder in London and an approaching snowstorm. When the lights come up, the audience sees the Great Hall of Monkswell Manor, which has been converted into the lounge of a guest house. Mollie and Giles Ralston enter and discuss their anxieties about starting their new venture as hotel managers without much experience. They had both been out on errands, and Giles wears an overcoat that matches the vague description on the radio.

Guests begin to arrive including Christopher Wren, Mrs. Boyle, Major Metcalf, and Miss Casewell. Christopher offers to help Mollie with cooking. An unexpected guest, Mr. Paravicini arrives; he claims his car ran into trouble in the snow.

The next afternoon, after a large amount of snow has fallen, Mrs. Boyle complains as Mollie does chores. Mollie receives a phone call saying the police are sending one Sergeant Trotter. Mollie tells everyone the police are sending someone, and Paravicini drops the fire poker and Metcalf freezes. Sergeant Trotter arrives on skis, tapping at the window. Once he is inside, Giles helps Trotter put away his skis, and Metcalf discovers the phone line is dead.

Trotter explains that the London murder investigation turned up a clue that mentioned Monkswell Manor. The murder victim was a foster parent at Longridge Farm where three Corrigan children were abused and one died. The prime suspect is Georgie Corrigan, one of the surviving children. Trotter questions everyone, but no one admits to being connected to Longridge Farm.

As Trotter tours the Manor, Christopher whistles “Three Blind Mice,” which was also mentioned in the clues that the murderer left. Metcalf reveals that Mrs. Boyle was a magistrate who sent the Corrigan children to Longridge Farm. When Mollie tells Trotter the phone line is dead, he asks Giles to check the upstairs extension and heads outside to follow the phone line. Mrs. Boyle winds up alone in the lounge and, after she greets someone offstage, a hand reaches into the room to turn off the light. In the darkness, the audience hears Georgie Corrigan (disguised as Sergeant Trotter) murder Mrs. Boyle.

Act II begins after Mrs. Doyle’s body has been moved. Everyone is in the lounge being questioned by Trotter. Giles accuses Christopher of the murder, but Mollie defends him. Mollie talks to Trotter alone and tries to accuse Metcalf and Paravicini. When Trotter leaves, Christopher returns and admits privately to Mollie that he is an army deserter.

Giles sees them talking alone together and becomes jealous. After Christopher leaves the room, Mollie confronts Giles about the newspaper, and he confronts her about a London bus ticket he found in her glove. Neither admits they were just buying anniversary presents. Trotter returns, looking for his skis. He questions everyone again, and Miss Casewell admits her name is Katherine and that she is using a false last name. Without saying it out loud, Trotter (Georgie Corrigan in disguise) guesses Miss Casewell is his sister (Katherine Corrigan), and she recognizes him as her brother. She starts crying and heads to her room.

Trotter gathers everyone one last time, asking that they reenact their movements during Mrs. Boyle’s murder. However, he has them switch places and gets Mollie alone. She admits she was the Corrigan children’s schoolteacher, but she did not receive Jimmy Corrigan’s letter in time to save him. Trotter confesses he is Georgie Corrigan and tries to kill Mollie.

Mollie is saved by Metcalf and Miss Casewell. The latter tells Georgie she is his sister, and he allows himself to be led upstairs by her. Giles returns and Mollie tells him about her past. Metcalf admits he was the real policeman all along. Giles reveals Paravicini is a watch thief. The play ends with Mollie and Giles confessing that they were in London buying each other anniversary presents. Metcalf discovers Mollie’s pie is burning in the kitchen, and the curtain falls.