Un Flic was Melville's last film and most crtics think his worst. That may be true but Melville's worst is better than most other directors best. The films opening sequence is also it's best, as four gangsters sit in an American car on a rainy French seafrount waiting to rob a bank. The robbery and the getaway are a masterpeace of economy with a minimum of dialogue but lots of atmosphere.
American actors Richard Crenna and Michael Conrad (Phil from Hill Street Blues) play two of criminals and Alain Delon plays the cop out to get them.
As with all of Melville's films the plot is secondary to the atmosphere and the way men, particulary criminals, relate to each other.
In a later robbery the bad guys rob a diamond smuggler on a moving train.
The special efects during this robbery are poor by today's standard and even by the standards of the time. Yet do not let this put you off. The action and figures may be stylised, all Melville's gangsters wear overcoats or raincoats, hats, drive American cars and drink wiskey, but the overall efect overides any faults. Melville was also always clear that his films were not intended to be a realistic portrait of the French underworld.
If you like your crime films blood soaked with massive gunfights and explosions then forget this film or any of Melville's others. If you want something a bit more inteligent give it a couple of hours.