A Guilty Thing Surprised, by Ruth Rendell

This is an Inspector Wexford mystery. A woman (Elizabeth) takes a walk in the woods at the grounds of her & her husband's (Quentin) estate, and winds up murdered. Inspector Wexford and his partner, Inspector Burden, talk with the husband, Elizabeth's brother & his wife, the employees of the estate and a few others. It is initially thought that Elizabeth was possibly having an affair, meeting someone in the woods, and when caught, was killed by either her jealous husband, or the gardener, Sean, who obviously had a crush on her. It turns out a little bit different, a surprising twist at the end. The great writing of Ruth Rendell makes her books hard to put down.