Part-time constable Ella Manning never thought she'd have to investigate her ex-fiance 's murder. But that's exactly what happens when tech entrepreneur Lincoln Shan is found dead in his study the morning after a controversial product launch - with the door locked from the inside. Trapped inside Shan's mansion above the remote town of Black Lake, it's up to Ella to catch the killer. But Black Lake is no ordinary place, and its strange history will make this the most baffling murder case of her career. Because some of the town's inhabitants have the power to rewind time - and someone is using it to protect a murderer. Just as Ella is sure she has identified the culprit, the last six hours are undone. With no memory of what she discovered before, her investigation begins again with very different results. But which conclusion was true? The race is on to find the killer before they strike again - and time is not on her side...