San Toy is the daughter of a mandarin but she has been raised as a boy to evade the consequences of a law drafting young ladies into a female regiment serving the Emperor. Her femininity is no secret, however, to Captain Bobby Preston, her naval lover, nor to Fo Hop his would-be Chinese rival. An elopement is forestalled by a new law drafting the sons of mandarins into the army. Rather than be called up, San Toy admits her sex and is put into the ladies' corps where she attracts the amorous attentions of the Emperor. But the stars conveniently decree that he should wed Wun Lung, a large perpetual corporal of the female guard, so San Toy is left free to wed her Bobby.