Durant els primers dies de la participació dels Estats Units a la Segona Guerra Mundial, un comboi internacional de 37 vaixells aliats, encapçalat pel comandant Ernest Krause, creua l'Atlàntic Nord mentre és perseguit per submarins alemanys.
Cop-turned-security guard Ma Xianyong finds himself in a criminal twilight zone when two unrelated events turn his world upside down. The mysterious disappearance of his boss has implications for his financial security. Even more perilous is the abduction of his paralyzed sister who, unknown to Ma, makes a morbid deal with her captors.