The basic plot is about Alice Tomaso (Paradis), a young car thief who is in search of her father. She finds out that both car dealer and former mercenary Léo Brassac (Belmondo) and businessman and former master thief Julien Vignal (Delon) are possibly responsible, and accidentally runs into the business of Russian mafia boss Anatoli Sharkov.
The following weapons were used in the film Half a Chance:
A Heckler & Koch MP5A3 is used by the Motorcycle Assassins in the beginning of the movie.
Mini Uzi
Besides the MP5, the Motorcycle Assassins also use at least one IMI Mini Uzi during the attack on the deal between Sharkov and Colombian drug dealer Angel Vargas (Luis Jaime-Cortez).
Thompson M1928
A Thompson M1928 submachine gun with a drum magazine is picked up by Julien in Léo's weapon chamber.
Several unidentified AK-47 variants are seen throughout the film.
SIG SG 543
The henchmen of Sharkov use several SIG SG 543 carbines with folding stocks during the final shootout.
SIG SG 540
Beside the more prominent SG 543, a SIG SG 540 rifle with a folding stock can also be seen.
Galil 7.62 ARM
When Alice frantically drives back to Léo's hideout, the Russian henchmen fire at her with a scoped Galil 7.62 ARM assault rifle.
Machine Guns
FN Minimi Para
A FN Minimi Para is used in the final shootout, distinguishable by its short barrel. Oddly enough, the top handle goes from being positioned upwards to being folded down along the handguard between shots.
Other Weapons
M72 LAW
In order to stop the dynamite-laden bulldozer driven by Léo, the Trenchcoat Killer orders the use of several M72 LAWs against it.
When they decide to face up with the Russians, Léo shows Julien into his arsenal. Many weapons can be seen here, including a Walther WA 2000 sniper rifle, several AK-47 variants, a FN MAG machine gun, a Stielhandgrante hand grenade and even a PIAT anti-tank launcher.