The House of the Arrow is a 1924 mystery novel by the English novelist A. E. W. Mason, the third full-length novel featuring his recurring character Inspector Hanaud. It has inspired several films of the same title. Plot After the death of Simon Harlowe, a wealthy art collector, his widow has continued to live in Dijon, latterly with her niece Betty and Betty's paid companion Ann Upcott. When Mrs Harlowe herself dies, her English solicitors receive a blackmailing letter from her brother-in-law Boris Waberski. He formally accuses Betty of poisoning Mrs Harlowe, and junior partner Jim Frobisher is dispatched to Dijon to provide legal advice. Waberski claims that Betty had bought poison from a shady herbalist, Jean Cladel, but is unable to make good his murder accusation. Mrs Harlowe's body shows no trace of poison, and it appears that she may have died of natural causes. But Inspector Hanaud is suspicious when on searching the house he finds in Ann's room a monograph describing Strophanthus Hispidus, a plant from which an undetectable arrow poison can be extracted. The book includes a plate of an actual arrow smeared with poison and an author's note thanking Simon Harlowe for lending it for research purposes. Although the house contains many treasures collected by Simon Harlowe, there is no sign of the arrow. Hanaud believes it to be in a suite of rooms that has been sealed by the police – Mrs Harlowe's downstairs bedroom and an interconnected "treasure room" used as Betty's sitting room. Betty says that on the night of Mrs Harlowe's death Waberski had been away for a few days. She had seen Mrs Harlowe shortly before leaving the house at 8:55pm to go to a dance, returning at exactly 1:20am (the time being noted by the chauffeur) and going straight to bed. She was woken by her maid Francine Rollard at 7:00 and told of the death. Ann says that she had fallen asleep in her chair, and had woken up after dark. Needing to check an address for a letter, she had gone downstairs to Betty's sitting room. Entering, she had flicked the light on and then quickly off again when she saw to her surprise that the interconnecting door leading to the bedroom, which was always locked, stood open. Through it she could hear voices and sounds that she interpreted as someone trying to sedate an intoxicated Mrs