Unexpected Guest

Imagine this scene: a traveler, whose car is stuck on the side of one of the coastal roads in South Wales due to dense fog, is searching for temporary shelter and help. But when he enters the first house he finds, he sees a woman with a gun in her hands, standing... over the body of her dead husband! She immediately confesses to committing the murder, but the traveler doesn't believe her for a number of reasons. He is convinced that the unfortunate woman is covering for someone. But who and why? These are the questions he must find answers to...