Mr Cassius has been married to his second wife, for four years now. Retiring to bed one evening, she urges him not stay up too much later, and he agrees. However, whilst readying herself for bed, she hears three loud shots fired. The only people in the house at the time were herself, Mr Cassius, and his secretary Mr Richards. The story begins with the occupants of the house being questioned by the inspector in charge of Mr Cassius' murder.