Is it possible that Martin Scorsese’s only Oscar winning film is his most underrated? When 2006’s The Departed finally landed the legendary director his first Oscars (it won Best Picture and Best Director), much of the conversation was about how the wins were more of a lifetime achievement award for a director whose best films were passed over decades ago: Taxi Driver in ‘76, Raging Bull in ‘80, Goodfellas in ‘90. While The Departed is not as iconic as those films, it’s still one of his best: a complex and perfectly paced crime thriller that deserves to be placed among the best American gangster films.

The Departed is a film about imposters and the impossibility of living two lives. Billy Costigan (Leonardo DiCaprio) comes from a broken family and dreams of becoming a street cop, yet is pressured by the police force into going undercover in the Boston mob led by Frank Costello (Jack Nicholson). Colin Sullivan (Matt Damon) is a poor Irish kid groomed by Costello from a young age to be a double agent in the state police. Both are trapped by circumstances, but Sullivan gets to buy a penthouse overlooking the capitol building while Costigan’s mental health slowly crumbles. The movie follows these two rats through the plot maze of double crosses, murders, investigations, and betrayals as the mob and the authorities struggle for control of Boston.

The Departed is based on the excellent Hong Kong gangster movie Infernal Affairs, but Scorsese makes The Departed his own, in part by grafting the story of infamous Irish mob boss (and FBI informant) Whitey Bulger on top of the script. Jack Nicholson plays Frank Costello as a pure piece of shit. He’s no match for Brando’s Vito Corleone or Pacino’s Michael, but he may be the antidote to the fantasy of a sauve and thoughtful Hollywood mob boss. Nicholson stomps around the film, hair askew and belly hanging out of his leopard print robe, cursing and assaulting with no pretense of gangster grace. “I don't want to be a product of my environment. I want my environment to be a product of me,” he snarls for the opening lines of the film.

Costigan and Sullivan want that too, but they aren’t as lucky. Like The Wire, The Departed shows how systems beyond the individual character’s control determine their fate.

The departed is fleshed out with a cast of stars given snappy if vulgar dialogue. Sullivan works for Alec Baldwin’s Captain Ellerby (“Our job is to smash, or marginally disrupt, organized crime in the city”), while Costigan’s only contacts are Martin Sheen’s Captain Queenan and Mark Wahlberg’s Staff Sergeant Dignam (“I'm the guy who does his job. You must be the other guy.”). Vera Farmiga plays Dr. Madden, the therapist and love interests of both leads, while Ray Winstone has a memorable role as Costello’s number 2, Mr. French (“I'm the guy who tells you there are guys you can hit, and there are guys you can't. Now that's not quite a guy you can't hit, but it's almost a guy you can't hit, so I'm fucking ruling on it right now that you don't hit him, understand?”)

Despite The Departed’s large cast and 150 minute run time, the film’s focus on the braided lives of Costigan and Sullivan—as well as Scorese’s editing—makes the The Departed a a far tighter film than his other acclaimed yet messy post-Goodfellas gangster epics, Casino, and Gangs of New York. The Departed takes a more complex look at law enforcement and organized crime than most mob films, layering the film with Catholic guilt and impossible moral choices. It is a film of ambiguity, with no happy resolutions for anyone.