Tras escapar de la que ha sido su prisión durante los últimos 13 años, Ivy Moxam realiza una llamada desesperada desde una cabina telefónica. Los agentes Carne y Merchant no saben cómo proceder con el caso, pero tras interrogar a Ivy se dan cuenta de que en realidad es quien dice ser.

Mientras se intensifica la investigación sobre niños desaparecidos, Ivy se ve presionada a revivir un pasado que preferiría olvidar. Mientras tanto, se confirma que ha sido Mark White el hombre que ha secuestrado a Phoebe.

As the police start to make breakthroughs in their investigation, Ivy turns to her sister Emma, who seizes the chance to connect with her. But they are interrupted by the arrival of a mysterious letter addressed to 'Alison' - White’s name for Ivy.

When evidence of Ivy’s DNA is all that is discovered in the cellar, she is arrested on suspicion of perverting the course of justice and taken into custody.

Ivy is forced to face her past and put herself at risk in order to save Phoebe. Carne and Merchant do everything they can to protect her, but in underestimating Mark White they have left their own lives hanging in the balance.