Beautiful British traveler, Jane Gershon, has a secret life. In the dangerous world of pre-WWI Europe, she is reputed to be a ruthless German Intelligence agent. When the war erupts, she is sent on a dangerous mission to Gibraltar. The British fleet is anchored in the waters of the strait, and Jane's mission is to gain entry into the British Naval Headquarters as part of a plot to destroy the fleet before it sails. Her treacherous plan works perfectly until the unexpected appearance of dashing Lt. Eric Woodhouse of British Intelligence. He and Jane had been lovers before her mission began and he knows she's not who she claims to be. But he doesn't suspect that she's an enemy spy!
A story of love and intrigue loaded with surprise turnabouts, Inside The Lines features an outstanding performance by Betty Compson as the glamorous, cold-blooded femme fatale. Her leading man, Ralph Forbes, was a well known Hollywood adventure hero on both the silent and sound screens, appearing in Beau Geste (1926), Beau Ideal (1931), The Three Musketeers (1935), Legion of Lost Men (1937), Kidnapped (1938) and many others.