Engineer Jake Holman arrives aboard the gunboat USS San Pablo, assigned to patrol a tributary of the Yangtze in the middle of exploited and revolution-torn 1926 China. His iconoclasm and cynical nature soon clash with the 'rice-bowl' system which runs the ship and the uneasy symbiosis between Chinese and foreigner on the river. Hostility towards the gunboat's presence reaches a climax when the boat must crash through a river-boom and rescue missionaries upriver at China Light Mission.

After World War II the crew of a motor gunboat join together to buy their old vessel and go into business for themselves. This may sound like a laudable scheme, but the business they choose to go into is smuggling.