After making a discovery during a routine drugs arrest, James 'Popeye' Doyle (Gene Hackman), an alcoholic but dedicated cop and his partner Buddy 'Cloudy' Russo (Roy Scheider) find that the culprit has a connection that could lead to a huge narcotics bust.
Later, while out at the pub, Doyle notes a meeting on a nearby table between well-known gangsters and Salvatore 'Sal' Boca (Tony Lo Bianco). He persuades Russo to follow Sal and his wife home, where it is established that they own far more expensive goods than their modest income should allow.
Doyle and Russo close in on The French Connection, but as the smugglers realise they're being watched, Doyle and Russo find themselves in ever increasing danger.
The French Connection was a real event of narcotics smuggling linked to the mob who transported opium from Turkey, transformed it into heroin in Marseilles, France before transporting it to the USA. Bizarrely, this practice was finally stamped out thanks to Turkish reform in 1971 - making William Friedkin's 1971 film very contemporary.
In fact, because the film was released in 1971, one can presume that its making was during the height of the French Connection and this is thoroughly shoved in the audience's face by the difficulty that Doyle and Russo face.
It is this difficulty in pinpointing the criminals that makes The French Connection a very gritty film. The culprit is hung out for the audience's attention at the beginning and we are forced to watch the bureaucracy hamper even the most determined cops. In fact, it the frustration of the system that enables us to fully empathise with them.
The French Connection is often remembered for its memorable chase sequence featuring Gene Hackman (or rather, his doubles) chasing down a subway train in a commandeered civilian car. It is this sequence alone that truly pushes The French Connection into the annals of movie history - probably aiding it no end to five 1972 Academy Awards.
Hackman, along with Clint Eastwood's Harry Callahan, pushed the 1970's as the start of the era of the maverick cop.