Snake in the Grass - Alan Ayckbourn

Miriam has cared for her father in the family home during his vituperative last years with the help of a creepily polite nurse, Alice. On Father's death, Miriam's older sister, handsome, divorced Annabel, comes home after over thirty years in Tasmania to find Daddy has left the bulk of his fortune to her. Alice complains to Annabel that Miriam has sacked her and is intent upon blackmail, having evidence, she says, that Miriam did away with the old man. Miriam and Annabel join forces against Alice and the blackmailer's body is soon hurtling down the well, but all does not end there.