A young Air Force veteran, Carrol Jo Hummer (Jan-Michael Vincent, Baby Blue Marine, TV's Airwolf), starts in business as the owner/operator of a thirteen speed, seven and one half ton diesel truck, which he dresses up and names the Blue Mule. With his bride, Jerri (Kay Lenz, Falling from Grace, Physical Evidence), he sets off to Tucson, Arizona, where his old friend Duane (Slim Pickens), the manager of a trucking company, gets him a job. But after Carrol Jo realizes he will be carrying illegal cargo and refuses the assignment, he's beaten by a band of gangsters working for an organized group of criminals headed by Cutler (Don Porter, 711 Ocean Drive). When Carrol Jo's commitment to staying honest results in even further violent retribution from the trucking syndicate, he has no choice but to team up with other independent truckers to break Cutler's stranglehold and uphold the rights of the decent working man.