The unexpected guest

When a stranger runs his car into a ditch in dense fog near the South Wales coast, and makes his way to an isolated house, he discovers a woman standing over the dead body of her wheel-chair bound husband, a gun in her hand. She readily admits to murder, and the unexpected guest offers to help her concoct a cover story. But is it possible Laura Warwick did not commit the crime after all? If so, who is she shielding? As the gallant unexpected gues...