The body of a 15-year-old is found hours after she sends a desperate message to her friends. It looks like suicide, until a second girl disappears. This time, the message is sent directly to the Metropolitan Police - and an officer's younger sister is missing. DS Nasreen Cudmore and journalist Freddie Venton will stop at nothing to find her. But whoever's behind the notes is playing a deadly game of hide and seek - and the clock is ticking.