Grace, a devoutly religious mother, has moved with her family to a mansion on the English coast, awaiting her husband's return from the war. Her two children both suffer from a rare photosensitivity disease that renders them extremely vulnerable to sunlight, prompting the rule of having only one door open in the house at a time. When one of the children claims to see ghosts, Grace at first believes her newly-arrived family of eccentric servants to be responsible, but as events become stranger, she begins to wonder if something supernatural is indeed going on.