Lucas Dale is the brash new owner of King's Bourne, the house where Cathy O'Hara and her cousin Susan grew up. Mousy, nervous Cathy works for Dale as a social secretary, while Susan is waiting for her fiance Bill Garrick to make his mark as an architect so they can marry. Lucas Dale, however, wants to marry Susan himself and uses her affection for Cathy to blackmail her into breaking her engagement and agreeing to marry him. At the same time, Dale's business partner from his shady past in America and his penniless first wife show up, making for very uncomfortable living conditions at King's Bourne. When Dale is found murdered in his study, there is no shortage of suspects. Unfortunately, the only one who was heard to vow revenge on the dead man is Bill Garrick, and Inspector Lamb and Sergeant Abbott have no choice but to go through his testimony with a fine-toothed comb.