The unexpected guest

Driving through dense Welsh fog, Michael Starkwedder runs his car into a ditch. After making his way to an isolated house, he discovers Laura Warwick standing near the dead body of her wheelchair-bound husband Richard, revolver in hand. She admits to murder, and her unexpected guest offers to help her concoct a cover story. But it is possible that Laura did not commit the crime after all ... If so, who is she shielding? The victim's mentally disabled half-brother? Her lover? Perhaps the father of the little boy Richard accidentally killed? The house seems full of possible suspects ...