From the bestselling author of What You Did comes a chilling story about a missing girl and two potential witnesses. They both think they saw her. But can they trust their own eyes? Mary hasn’t slept in what feels like years. Her two young children never let her rest, and so one exhausting night, in the middle of a London heatwave, she escapes to a nearby park for some air. Tim can’t sleep. It doesn’t feel safe after the terrible thing that happened to him. Seeking solace outside, he encounters a sleepless Mary in the park. There, the two strangers witness what looks like a violent attack in the window of a neighbouring house. Shocked at what they’ve seen, Tim and Mary form an unlikely bond, desperate to find clues. When they see news reports of a missing woman, who was last seen walking alone not far from them, the pair are convinced it’s her they saw being attacked. The police don’t believe them, but when they hear of a potential link to an old murder and a string of disappearances from the area, pressure mounts to find her before it’s too late. But with her marriage under strain and the police on their tail, Mary begins to doubt her own mind…and Tim’s. How reliable is a man who doesn’t sleep? As the pair are drawn into a dangerous game of cat-and-mouse, the culprit appears to be even closer to home than they thought. Have they got it all wrong, or is something even more sinister going on?