When young Sarah drowns off the rocky coast of Wales, her distraught parents, James (Sean Bean) and Adele (Maria Bello), search in vain for their child's missing body. But when a mysterious young girl tells her she's looking in the wrong place, Adele recalls the legend of The Dark, the Celtic land of the dead. Haunted by ghastly visions of Sarah pleading for help, Adele becomes convinced of the legend's truth...and as James watches in horror, Adele embarks on a journey beyond madness as she invokes the ancient rule of return: one of the living for one of the dead.