Police At The Funeral by Margery Allingham

In this classic mystery novel, the enigmatic detective Albert Campion is called to the ancient and oppressive house of the Faraday family in Cambridge to investigate a series of sinister events. The once-respected family is plagued by a string of murders, each more baffling than the last, and Campion must navigate the labyrinth of secrets, lies, and old grudges that haunt the household. As he delves deeper into the family's dark past, Campion uncovers a web of intrigue and deception that threatens to destroy them all, leading to a gripping and unexpected climax.