A man wanders into a remote house on a foggy night only to find a woman standing over her husband's dead body with a gun in her hand. The protagonist, Michael Starkwedder, must navigate the immediate aftermath of this discovery while deciding whether to protect the woman, Laura Warwick, or expose the truth. The narrative unfolds within the claustrophobic confines of a Welsh estate, where the interplay of secrets, past grievances, and shifting loyalties creates a high-stakes environment. As the investigation proceeds, the play utilizes a classic whodunit structure to challenge the audience's perception of guilt and innocence.

This work is widely recognized as one of Christie's most effective stage plays, praised for its ability to maintain suspense within a confined theatrical space. The premise suggests a classic exploration of the 'whodunit' genre, where the focus remains on the intricate web of lies spun by the household members. Readers and audiences often note the sharp, economical dialogue that defines Christie's dramatic writing style. The play is frequently cited for its clever subversion of audience expectations regarding the initial crime scene.