Children often dream of discovering lost treasure. The dreams become a reality when a mischievous nine year old boy named Peter, through a series of amazing coincidences, become entangled in the legacy of a deeply disturbing war-time drama while on holiday in Norfolk during the summer of 1948. With help from his school friend Andy and a girl called Meg, they uncover the identity of a dangerous German spy who unwittingly leads them to find a missing presumed dead British Naval Commander and the recovery of a valuable cache of diamonds.