The Mousetrap is Agatha Christie's famous murder mystery play, known as the longest-running play in history, about a group of strangers trapped in a snowbound guesthouse where a murderer is among them. Originally a radio play called Three Blind Mice, it was expanded and opened in London in 1952, becoming a record-breaking phenomenon. The plot involves classic whodunit elements like red herrings, eccentric characters, and a famous twist ending, with the killer's identity kept secret from the audience.