Trial by fury

Review from Amazon dot com: "Sixty-year-old Constance Lawley takes on temp housekeeping jobs as a way of keeping busy. She likes people and enjoys helping them. Her job involves running households in which someone is recovering from injury or illness. Her latest assignment is working for a charming old couple with a grandson who’s not quite normal. It looks like one of her easiest and most pleasant job — until she walks into the living room after grocery shopping and finds four dead bodies. It’s a massacre — and another person will soon be murdered too."