Jim Young of Youngstown, Pennsylvania, reads of the German war atrocities and decides to enlist in the British army, thus becoming a forerunner of the American forces that are subsequently to leave for the battlefields of Europe. He begins active training at a camp outside London. While enjoying a few hours of leave, he meets Susie Broadplains , a young woman from Australia. She is flattered by his attentions and their friendship soon blossoms into love.

However German plotters plan to destroy an arsenal at night and Sir Roger is inveigled into driving an automobile along a London road with its lights turned skyward to guide the Zeppelins. Jim, wounded and home on furlough, detects Sir Roger on the lonely road, follows and traps him in his cottage. Sir Roger turns his pistol on himself rather than be taken alive. Susie finds the "great love" in service for the cause of democracy and her country, with a greater love in sight.