What happens in The Mousetrap?
The setting is Monkswell Manor, a Victorian country guesthouse in rural England, just opened by newlyweds Mollie and Giles Ralston. A snowstorm cuts the house off from the outside world on the same evening that the first paying guests arrive. News reaches the guesthouse that a murder has been committed in London — and that the killer is suspected to be heading towards Monkswell.
The guests
The visitors arrive in turn, each carrying a piece of suspicion. The architect-trained Christopher Wren, who behaves with theatrical flamboyance. Mrs Boyle, an unyielding retired magistrate. Major Metcalf, a stiff-backed military man. Miss Casewell, a cool young woman with an unspecified past. Mr Paravicini, a flamboyant continental who arrives unbooked, claiming his car has overturned in a snowdrift. None of their stories quite add up.
The detective and the murder
Detective Sergeant Trotter arrives on skis, having struggled through the snow to reach the house. He explains that the London murder is connected to the abuse of three children at a farm during the Second World War; the killer is taking revenge on those they hold responsible. One name on the list is at Monkswell. The phone lines go dead. The lights flicker. Before the act break, one of the guests is murdered. Everyone is a suspect.
The ending
The play closes with a reveal that the audience has, by long tradition, been formally asked not to disclose. The convention has held since 1952 with remarkable success — the ending of The Mousetrap is one of the most thoroughly preserved twists in any form of popular culture. A film adaptation cannot, by contractual agreement, be made until six months after the play's West End run ends. So far, that condition has not yet been met.
How The Mousetrap became the longest-running play in history
The birthday-gift origin
The Mousetrap began as Three Blind Mice, a 30-minute radio play Agatha Christie wrote in 1947 as a gift for Queen Mary's 80th birthday. The BBC broadcast it on 30 May 1947. Christie expanded it into a stage play in the early 1950s; the title was changed to The Mousetrap (a reference to Hamlet's play-within-a-play) to avoid confusion with a then-active short story of similar name.
The 1952 opening
The Mousetrap opened on tour in Nottingham in October 1952 with Richard Attenborough as Detective Sergeant Trotter and Sheila Sim (Attenborough's wife) as Mollie Ralston. The London premiere followed at the Ambassadors Theatre on 25 November 1952. Christie herself reportedly told her son-in-law she expected the run to last "perhaps eight months." It did not stop.
The 1974 transfer
In March 1974, after 21 years at the Ambassadors, the production transferred across West Street to St Martin's Theatre — the larger of the two adjoining theatres that share a wall (both designed by W.G.R. Sprague). The transfer was managed without a break in the run: the final Ambassadors performance and the first St Martin's performance were on consecutive nights. The play has been at St Martin's ever since.
The pandemic pause and return
For the first time in 68 years, The Mousetrap was forced to suspend performances when London theatres closed in March 2020 because of the COVID-19 pandemic. The production returned to St Martin's Theatre in May 2021 — the official restart of its uninterrupted run. The producers maintained that the show technically retained its world-record status as the longest continuous theatrical production, as the closure affected the entire West End equally.
The 2022 Olivier and 2025 milestone
In 2022 — the play's 70th year — The Mousetrap received a Laurence Olivier Award for Special Recognition. In 2025, the production celebrated its 30,000th West End performance. Producer Brian Fenty took over from Adam Spiegel in 2024, with the play now in its 75th anniversary year.
The new 2026 cast
From 11 May 2026, the production introduces a new West End company. Saranna Parlone (Mollie Ralston) and Ben Riddle (Giles Ralston) are both promoted from understudy roles in the existing company. Ben Galvin (Runaway) takes the pivotal role of Detective Sergeant Trotter. The remaining company is completed by Nancy Doubledee, Bella Farr, Barnaby Jago, Richard Parnwell and Clive Marlowe. Booking now extends through to 3 January 2027.
