Ruth is in London clearing out her mother's belongings when she makes a surprising discovery: a photograph of her Norfolk cottage taken before Ruth lived there. Her mother always hated the cottage, so why does she have a picture of the place? As she died three years ago, Ruth can't exactly ask her, and her father denies all knowledge of the picture. The only clue is written on the back of the photo: Dawn, 1969. Ruth returns to Norfolk determined to solve the mystery, but then Covid-19 rears its ugly head. Ruth and her daughter are locked down in their cottage, attempting to continue with work and lessons, but, in reality, becoming lonely and frustrated. Happily the house next door is rented by a nice woman called Sally, who they become friendly with while standing on their doorstep clapping for carers. Nelson, meanwhile, has no time to be bored. He's investigating a series of suicides that could be the work of a serial killer. It's only when he links them to an archaeological discovery that he thinks of Ruth. He breaks curfew to visit the cottage to find Ruth chatting to her neighbor, whom he remembers as Dawn Lancaster, a carer who was once tried for murdering her employer. When the deaths continue, Nelson vows to take Ruth and Kate to live with him. But they, and Dawn, have vanished.