When Claire Cooper was eight years old her mother mysteriously vanished during Hop-tu-naa, the Manx Halloween. At fourteen, Claire is still struggling to come to terms with her disappearance when she's befriended by a group of five teenagers who mark every Hop-tu-naa by performing dares. But Claire's arrival begins to alter the group's dynamic until one year a prank goes terribly wrong, changing all their futures and tearing the friends apart. Six years later, one of the friends is killed on Hop-tu-naa in an apparent accident. But Claire, now a police officer, has her doubts. Is a single footprint found near the body a deliberate taunt?.