An old friend of Lovejoy's asks for help when her wartime sweetheart, a Czech pilot who was presumed killed in action, reappears after fifty years. The man has returned to England to collect a cache of gemstones that were buried in the grounds of a church, but he is killed when he tries to retrieve them. Discovering that the diamonds were looted from Prague during the war, Lovejoy and Eric travel there on the trail of the jewels and encounter sinister forces who also want the jewels and are prepared to murder to get them.