The outbreak of World War I places Scots officer Geoffrey Richter-Douglas in an uncomfortable position. Although his allegiance is to Britain, his mother was from an aristocratic Bavarian family, and he spent his summers in Germany as a child. When Geoffrey is approached by a German spy who offers him a chance to defect, he reports the incident to his superiors, but instead of arresting the spy they suggest that he accept her offer--and become an Allied agent. In Germany, among old friends, Geoffrey discovers that loyalty is more complicated than he expected, especially when he finds himself aboard the maiden voyage of a powerful new prototype Zeppelin, headed for Scotland on a secret mission that could decide the outcome of the war.

Phillip Calvert is a British Treasury secret service agent assigned to stop the ruthless pirating of millions in gold bullion off the western coast of the Scottish highlands. His search takes him to the small port town of Torbay on the Isle of Torbay where numerous fishing boats, yachts and people have been mysteriously disappearing. A trail of deceit and subterfuge leads him to Cypriot tycoon and shipping magnate Sir Anthony Skouras and his beautiful wife, Charlotte aboard their luxury yacht anchored off the coast, who may hold the answers to the truth.