Not all journeys by post box have happy endings. Not all heroes know that. Close to her home, nearly twelve-year-old Claudia Salter stumbles upon a strange woodland clearing whilst exploring the languid summer countryside. The other-worldly clearing reveals a mysterious, old-fashioned, red post box basking in the sunlight. Very soon, Claudia comes to realise that this post box must be connected to the unexplained vanishing of a local boy, who was lost from a nearby town sixty years previously. Returning to it, Claudia is propelled by the post box to a place she cannot believe exists, and it is there that she uncovers the sinister and malevolent reasons for the boy's disappearance. Acutely aware of her dangerous predicament, Claudia has to harness her new found inner strength and, together with some unlikely allies, she has to face up to the significant danger that imperils them all.