Lyon Gaultier's brother gets murdered after welshing drug associates in Los Angeles. Lyon is in North Africa serving the last six months of a hitch in the French Foreign Legion when he gets word of the incident, and he unsuccessfully petitions his cold-blooded superiors for leave to tend to family matters. Desperate, Lyon knocks several legionnaires out and stows away on a steamer headed for America. Once Lyon gets near New York harbor, Lyon jumps ship and tries to come up with a way to get enough money to head for California. Lyon comes into contact with street-fight promoter Joshua, an alcoholic ex-street-fighter who links Lyon up with Cynthia, an organizer of no-holds-barred bare-knuckle fights that secretly entertain the wealthy across the country. The minute Lyon makes it to Los Angeles, Lyon finds that his brother's killers are in police custody. Lyon is soon fighting various contenders — ranging from a Scotsman in a kilt to a long-haired surfer — earning money to help keep bill collectors away from the door of his widowed sister-in-law Helene and his niece Nicole, who comes to love him. Although Lyon only wants to bash opponents long enough to gain enough money to assist Helene and Nicole, Cynthia is reluctant to let go of her new meal ticket. Helene blames Lyon for not helping his brother sooner, But Lyon keeps fighting and secretly sends her money in the guise of an insurance policy that she didn't know about. Cynthia decides to import a killer-fighter named Attila to polish Lyon off. Not only does she bet against Lyon, she also schemes to turn him over to the Foreign Legion after Atilla beats him. But Lyon has other plans. And there is also a pair of men from the Legion who have been assigned to find Lyon and bring him in.
- When the streets are a jungle...there can only be one king.
Honour or revenge, he has no choice...
- Too tough to die.