The crew of a Royal Naval expedition searching for the Arctic's treacherous Northwest Passage discovers instead a monstrous predator.

When former detective Robert and his school teacher wife Katy decide to make major changes to their lifestyle, they impulsively purchase a guest house in the Lake District where they plan to create a haven for holidaymakers. When Mark, a former colleague and friend, approaches the couple asking for their help in providing temporary housing for people needing protection from criminals, their idyllic guest house quickly becomes a safe house.