With “”Goodfellas”” and “”Mean Streets,”” Martin Scorsese was pretty much the unofficial king of mobster movies and Robert De Niro was president of its fan club. Even though De Niro isn’t there this time around, Jack Nicholson puts grit back into the street life with Scorsese’s latest movie, “”The Departed.””

Billy Costigan (Leonardo DiCaprio) and Colin Sullivan (Matt Damon) are almost living the same life – both are blond, ambitious and attending the same police academy. That’s about all they have in common.

Sullivan, despite his clean-cut looks, is actually a mole placed into the Special Investigation Unit by the Boston mob boss Frank Costello (Jack Nicholson) to keep the cops from getting too close on his tail.

Costigan, who comes from a rather shady past, is used by the police force to go undercover as a mobster in Costello’s gang. Costigan is put into the crew for indefinite period of time to try to find out enough information so law enforcement agents can finally bring Costello down.

The plan goes awry, however, when Sullivan finds out through his job that the mob has been infiltrated by a spy. He then tips off his real boss, Costello. When Costello starts trying to flush out the rat, Costigan in turn lets the police know that they, too, have someone on the inside. With both sides trying to figure out where the leaks are coming from, neither Costigan nor Sullivan is safe. The question becomes which one is willing to go the furthest to make sure he isn’t discovered first.

“”The Departed”” is an action thriller to the max. It’s got the shooting and dead bodies dropping from the sky (quite literally), but it also works on the suspense level. With both sides trying to find the liar in the midst, the scenes work in achieving an incredibly palpable tension.

Much of that is thanks to DiCaprio; his paranoid gestures and twitches go a long way for spreading the fear. He makes it so you realize how much is at stake if his character is found as being the police spy in the mob – a not-so-pretty ending. Even the viewer can’t feel at ease.

Nicholson as Costello is incredibly convincing as a mobster. He channels his rage and craziness, which makes the mob boss come off as almost as creepy and insane as his old character from “”The Shining.”” Every opportunity the filmmakers are presented with, they build up his dementedness. When Costello has to take someone out, he laughs maniacally the whole time. He’s always about five seconds away from that famous “”Here’s Johnny”” moment.

“”The Departed”” is anything but an enlistment video for signing up for the Boston mob. Shootouts, stranglings and routine beat-downs make for a rather perilous job, but it’s definitely something you’ll want to watch – from the outside.