When her marriage breaks down, Mel returns from Australia to the UK, and moves into the family home with her twin, Abbie. Mel just needs some space so she can recover from a painful separation and get ready to begin a new phase in her life. But something isn’t right… The twins have always been close, but Abbie seems like a different person. She used to be outgoing and gregarious, now she’s sullen and hostile. Even worse, a sinister man Mel has never seen before is following her. She doesn’t know what he wants, but she’s pretty sure it’s nothing good. And Mel is right to be worried. As she is inexorably pulled into a vortex of unimaginable terror, she discovers the horrifying truth about Abbie’s secret life… And the terrible price that has to be paid – by the wrong twin.