Lights, camera, action!
In the port city of Marseille, France, an undercover detective follows a known criminal.
The man, named Pierre Nicoli, is the henchman of a silver-haired drug kingpin named Alain Charnier. Charnier and Nicoli partner with a movie star in order to get a half-million dollar shipment of pure heroin overseas to New York, hidden in a Buick Mk III. The movie star will travel with the car across the Atlantic, while supposedly in pre-production for a film.
Confused yet? Don't worry—it's way easier to follow when you're watching the action unfold in glorious '70s Technicolor.
Meanwhile, a boozing, lady-chasing, rageaholic cop named Jimmy "Popeye" Doyle has a hunch that something major's about to go down in Brooklyn. When he's out one night after a rough day at work, with sober, even-keeled Buddy "Cloudy" Russo, he notices a candy shop owner with minor criminal ties named Sal Boca passing out cash like it's going out of style.
When they tail him, the partners learn that Sal is connected to a major drug deal financier, and they plead with their captain to let them get phone taps and warrants. After their captain pairs them with a duo of Federal agents—even-Steven Klein and antagonizing Mulderig—Cloudy and Popeye get to work.
When the movie star arrives in New York with his drug Buick, so do Charnier and Nicoli. Sal and his money-man get to work with the Frenchmen, aware that they're being tailed by the four detectives the entire time. The tail makes Charnier nervous, and he's eager to get the deal done.
Meanwhile, Nicoli decides that he has to get rid of Popeye… and in doing so kicks off one of the most famous chase scenes in the history of cinema. Nicoli takes control of a subway train, and Popeye follows in a car underneath the elevated tracks.
Just...watch.
(In the end, he offs Nicoli when his back is turned.)
The death of Nicoli makes Charnier even more impatient, while Popeye can't brush off the feeling that something's "dirty" with that Buick that the French movie star brought over. When they're finally able to get their hands on it, they take it into the forensics garage and strip down, eventually finding the heroin, confirming what Popeye thought all along.
They return the car, saying it must have been stolen, and the shaken movie star proclaims to Charnier that he's done with the whole thing. Sal picks up the car with Charnier in it, and they head to some abandoned buildings under the Roosevelt Bridge to finally get the deal done.
The crooks do their deal, all but high-fiving each other, and then head back to Manhattan. But Popeye and the guys have set up a roadblock with half a dozen cop cars. They turn tail to warn the others, and Cloudy shoots Sal dead while everyone but Charnier gets scooped up and cuffed. Popeye runs into a building after Charnier and shoots, accidentally killing Mulderig.
He's not fazed.
He continues his chase. We hear another shot go off...and the screen cuts to black.