Inspector Lynley Mysteries: A Suitable Vengeance (2003)

It's a tension filled weekend for Tommy Lynley when he and Helen go the family estate to hold their engagement party. Tommy is estranged from his mother owing to the time he found her in bed with their family physician, Dr. Trenarrow, while his father was dying of cancer in the next room. He's on less than good terms as well with his brother Peter who feels that Tommy abandoned him when their father died. When Mick Cambrey is found dead in his shop in the village, the police arrest his father-in-law John Penellin, the Lynleys long-time estate manager. Lynley and Haver soon determine that the death is related to drug smuggling. When one of the weekend guests, Justin Brooke, is found dead on the estate, they realize something other than heroin was being smuggled.