2005: 17 year old Ellen falls under the spell of glamorous newcomer, Sasha. As Ellen is welcomed into Sasha's family, she doesn't see the darkness that lies beneath their musical, bohemian lifestyle. At a New Year's Eve party, events come to a dramatic head, resulting in a court case (in which Ellen is a key witness) that means family life at the Corner House will never be the same again.

2018: Now 30, Ellen and Sasha are still entwined in each other's lives and sharing a flat in London. When Sasha disappears, Ellen fears the worst. She has gone missing like this before and the police won't take it seriously, but long-buried events in their shared past mean that Ellen has good reason to be frightened - not only for Sasha, but also for herself. Finding out the truth about what really happened on New Year's Eve twelve years ago puts Ellen in terrible danger, and forces her to confront not only the past, but how well she really knows her best friend.