In the American Southwest, Jim Kane (Paul Newman) scrapes a living as a cowboy. The trouble is, something always seems to go wrong. His latest job concerns transporting a herd of cattle from Mexico into the United States for shifty businessman Bill Garrett (Strother Martin). But Kane knows it won't be easy -- he only just lost money when the horses he tried to bring over were quarantined by customs. Desperate for pay, he goes ahead anyway, teaming up with his old partner, Leonard (Lee Marvin).