Four Days' Wonder by A. A. Milne

Jenny Windell is obsessed with murder mysteries, so when she discovers her estranged aunt dead at her country home, the stage is set for her own investigation.

Worried that being the first at the scene of the crime will make her a suspect and ruin her inquiry, she flees. On the run, she befriends Derek Fenton, the dashing younger brother of acclaimed crime writer Archibald Fenton, and persuades him to join her in her attempts to solve the crime and outsmart dim-witted Inspector Marigold.

An affectionate send-up of the classic Golden Age murder mystery, this charming comedy is A. A. Milne at his most delightful.