Crooked House
Agatha Christie
 Three generations of the Leonides family live together under wealthy patriarch Aristide. His first wife died; her sister Edith has cared for the household since then. Second wife indolent Brenda, decades his junior, exchanges love letters with grandchildren's tutor. After Aristide is poisoned by his own eye medicine (eserine), his granddaughter Sophia tells narrator and fiancé Charles Hayward that they cannot marry until the killer is apprehended. Charles' father "The Old Man" is the Assistant Commissioner of Scotland Yard, so Charles investigates from the inside along with assigned detective, Chief Inspector Taverner. When sly Josephine suffers attack and Nanny is poisoned by hot chocolate after Brenda and the tutor are arrested, the danger escalates to a surprise finish.