Sick of Shadows (Edwardian Murder Mysteries, #3)

Lady Rose Summer and Captain Harry Cathcart have an engagement of convenience to keep her from India and failed debutantes. She befriends newly arrived Miss Dolly Tremaine, stabbed to death and floating in a boat on the Serpentine River, and barely survives an attempt on her own life. Harry is summoned and the duo uncover deceptions, secrets, and the killer.