Just back from maternity leave, forensic archeologist Ruth is finding it hard to juggle motherhood and work when she is called in to investigate human bones that have surfaced on a remote Norfolk beach. The presence of DCI Harry Nelson, the married father of her daughter, does not help. The bones, six men with their arms bound, turn out date back to World War II, a desperate time on this stretch of coastland.

Home Guard veteran Archie Whitcliffe reveals the existence of a secret the old soldiers have vowed to protect with their lives. But then Archie is killed and a German journalist arrives, asking questions about Operation Lucifer, a plan to stop a German invasion, and a possible British war crime. What was Operation Lucifer? And who is prepared to kill to keep its secret?