Nest of Vipers — Gladys Mitchell

The tenants of Weston Pipers are horrified to discover that one among them, the reclusive Miss Minnie, has been elaborately and violently murdered, and that their young landlord, Chelion Piper, is the chief suspect. Piper is advised to write down his version of events for the noted criminologist and psychoanalyst Dame Beatrice Bradley, as her investigations uncover a junk shop with a secret room, a possible satanic cult and a veritable nest of vipers