The Departed ending explained: who dies, why Dignam shoots Sullivan, and the rat
Spoilers ahead: this article discusses the ending.
The Departed ending explained: undercover cop Billy Costigan arrests mob mole Colin Sullivan but is shot dead in an elevator by a second mole, Trooper Barrigan. Sullivan kills Barrigan to cover his tracks and walks free, until Sergeant Dignam shows up at his apartment and shoots him.
Martin Scorsese's 2006 remake of the Hong Kong film Infernal Affairs won Best Picture, and its final ten minutes are among the bleakest in a mainstream crime film. Here is what happens, what the closing image of the rat means, and how the film's motifs set it all up.
The Departed ending explained: what happens
After Costello is killed, Costigan goes to Sullivan expecting his identity to be restored but spots Costello's envelope on Sullivan's desk and realises Sullivan is the mole. Costigan flees, and Sullivan deletes Costigan's police records. Costigan leaves evidence with Madolyn Madden, the psychiatrist both men are involved with, including recordings of Sullivan talking with Costello.
Costigan meets Sullivan on the rooftop where Captain Queenan died and arrests him. Trooper Brown arrives, and in the lobby elevator Trooper Barrigan shoots Costigan, revealing he is another of Costello's spies. Barrigan shoots Brown, and Sullivan shoots Barrigan, framing him as the only mole.
Why Dignam kills Sullivan
Sullivan recommends Costigan for a posthumous commendation. After the funeral, a pregnant Madden leaves him; she has heard the tapes. Sullivan comes home to find Dignam waiting. Dignam, suspended earlier after confronting Sullivan, shoots him and leaves.
Dignam is the only person who knew Costigan was undercover and who distrusted Sullivan from the start. With the evidence trail broken and Sullivan protected by his rank, the law will not reach him, so Dignam delivers the justice the system cannot. One reading notes the irony that the man who exposes the mole ends the film committing the same kind of killing as the gangsters.
What the rat means
In the final shot, the camera moves from Sullivan's body to the window, where a rat runs along the railing with the gold dome of the Massachusetts State House behind it. Scorsese has acknowledged that it is not meant literally but symbolises the film's search for the rat and the distrust between characters, which he likened to post-9/11 America. The view behind it also nods to gangster films like Little Caesar, Scarface and White Heat.
Some critics found the image too blunt. It works best as a reminder that removing one informant does not clean up the system; the dome in the background suggests the corruption reaches the institutions themselves.
The X motif that predicts every death
Scorsese borrowed a device from Howard Hawks's 1932 Scarface, placing an X in the frame before characters die. The film is full of them once you know to look.
- Cross-beam supports in an airport walkway while Costigan phones Dignam.
- Taped windows on the building Queenan enters before he is thrown to his death.
- An X behind Costigan's head in the elevator before he is shot.
- The carpet pattern in Sullivan's hallway before Dignam kills him.
How it differs from Infernal Affairs
Warner Bros. bought remake rights for $1.75 million, and William Monahan moved the story to Boston, basing Costello on Whitey Bulger and his relationship with the FBI. That changes the ending's meaning: Costello himself is revealed as an FBI informant, so almost everyone is playing both sides. In Scorsese's version nobody escapes, and Madden's exit past Sullivan at the funeral quotes the closing shot of The Third Man.
Questions people ask
Who is the second mole in The Departed?
Trooper Barrigan, who shoots Costigan in the elevator and is then killed by Sullivan.
Why does Dignam kill Sullivan?
Because Sullivan covered his tracks and would never face justice. Dignam knew Costigan was undercover and suspected Sullivan.
What does the rat at the end mean?
Scorsese said it is not literal but reflects the hunt for the rat and the pervasive distrust among the characters.