Death and the Dowagers by Tony Brennan

Spring of 1952. Annie Watson, now widowed, is assisting her daughter Lady Penelope Sheridan with the first formal dinners to be held at the renovated Big House. Even the reputedly troublesome Dowager Lady Edwina cannot cast a shadow over the triumphant success of the first dinner. But in all the planning, none of them expected murder to be served as one of the courses. With the ever-loyal assistance of Superintendent Peters and team, Annie inveigles Edwina into the murder investigation. Little does she know she will involve the Dowager in a hair-raising confrontation with a serial killer — as an after-dinner mint!