From the second they set foot on the island to join their dad and his new family, Jess and Rosie feel that something's wrong. Nightmares haunt their dreams and there seems to be someone, or something, else with them in the lighthouse - their home for the summer. Counting down the days until they can leave, Jess and Rosie decide to investigate. But when Rosie disappears, the countdown takes on a new meaning. Especially when no one but Jess remembers Rosie at all...