In the former mining town of Black Lake on the west coast of Canada, there is a story about a shipwreck. All those aboard died, except an unnamed man who staggered ashore. His descendants have a unique ability: once in their lives - and only once - they can unwind the events of the previous six hours. More than 200 years later, Ella Manning, marine biologist and part-time police constable, is attending a party at Black Lake Manor, the cliff-top mansion of the town's divisive local billionaire. With a raging storm coming in from the Pacific, she and several other guests find themselves trapped. And when their host is discovered murdered in a locked room, they turn to her to solve the crime. Against the odds, Ella is sure she has identified the killer - but then time is unwound. With no memory of what she discovered before, her investigation begins again, with very different results.