Jane Gershon is engaged to Eric Woodhouse, living in Germany prior to the onset of World War I. When the war breaks out, they are forced to separate, but are reunited months later in Gibraltar, at the British fortress there. Both are supposedly German spies with orders to destroy the British fleet, anchored in the harbor. Not fully trusting either of them, the German government has sent another agent, the Hindu Amahdi, to ensure that their sabotage plans are carried out. Both Jane and Eric believe the sincerity of the other as a German agent. When it appears that Jane's attempt to destroy the fleet is uncovered, to save her, Eric takes the blame and seemingly commits suicide. However, when Ahmadi uncovers the truth that Jane is really a double agent for the British government, he attempts to go through with the sabotage. When he is about to kill Jane, Eric reappears and kills him. Jane discovers Eric is also a British double agent and they are happily reunited.