During the First World War, British soldiers Bert and Erb attempt to thwart an enemy agent on the streets of London, before sailing on a troop ship to Mesopotamia, where they join in the trench warfare against the Turks. Later they dress as harem girls to sneak into the Caliph's palace, where they use a magic show to trick their way to victory. They return to England and marry their beloveds, and Erb wins the Victoria Cross.