1926 China. Engineer Jake Holman is transferred to the USS San Pablo, a gunboat patrolling the troubled waters of the Yangtze River. As Chinese factions battle around them, the crew has one singular mission: to protect American interests in the region... without provoking an international incident. But as hostility over the U.S. presence in the river intensifies, Holman and his sole ally know their latest assignment - to save a U.S. missionary - could be their last!