A Suspension of Mercy (Random Acts of Kindness)

Patricia Highsmith, Joan Schenkar

Television scriptwriter Sidney Bartleby, who specialises in murder mysteries, daydreams about killing his wife, Alicia, as a way of drawing inspiration for his stories. However, when she unexpectedly takes a long holiday away from him, he begins wondering whether he could ever put his plan into action. Also published as Suspension of Mercy. From Wikipedia