Doctor Tony Craig (Chester Morris) pursues an old flame, nurse Ann Grayson (Wendy Barrie), aboard the SS Arcturus, bound from Shanghai to San Francisco. Challenging Craig's courtship is Crusher McKay (Victor McLaglen), the ship's chief engineer. The rivalry comes to a sudden halt when it's revealed a Chinese stowaway has unknowingly brought along a passenger -- cholera. As the disease ravages its way from below deck towards the passenge