Short answer: almost nobody survives. In the final ten minutes of Martin Scorsese’s The Departed (2006), undercover cop Billy Costigan finally arrests mole Colin Sullivan — only to be shot dead in an elevator by a second, hidden mole. Sullivan then kills that man, frames him as the traitor, and walks away believing he has won. He has not: Sergeant Dignam waits in his apartment, and the last shot is a rat on the balcony railing.
Spoiler Recap: Two Rats in the Same City
The Departed, a remake of the 2002 Hong Kong thriller Infernal Affairs, is built on a mirror image. Billy Costigan (Leonardo DiCaprio) is a Massachusetts State Police officer sent undercover into crime boss Frank Costello’s (Jack Nicholson) South Boston crew. Colin Sullivan (Matt Damon) is Costello’s man planted inside the police, rising through the ranks as Costello’s informant. Each is a “rat” betraying his own side. Queenan (Martin Sheen) and Dignam (Mark Wahlberg) run Costigan; Madolyn (Vera Farmiga) is involved with both men. When Sullivan discovers Costello himself has been informing to the FBI, he arranges a raid and finishes off a wounded Costello. Costigan should now be free, but Queenan is already dead — thrown from a rooftop by Costello’s men — and Dignam is suspended, leaving Costigan stranded undercover.
The Ending, Scene by Scene
The tape. After Costello’s death, Costigan receives a recording of Sullivan’s conversations with Costello — proof Sullivan is the mole. He makes copies, mails one to Sullivan, and sends the evidence to Madolyn.
The rooftop. Costigan meets Sullivan on the rooftop where Queenan was killed and arrests him at gunpoint: “I’m the guy who does his job. You must be the other guy.” He calls Trooper Brown (Anthony Anderson) for backup and cuffs Sullivan.
The elevator. In the lobby, the elevator doors open — and Trooper Barrigan (James Badge Dale) shoots Costigan in the head, then kills Brown too. Barrigan tells Sullivan he is also one of Costello’s moles.
Sullivan’s cover-up. Sullivan immediately shoots Barrigan dead and pins everything on him, claiming Barrigan was the mole all along. He even recommends Costigan for a posthumous commendation — a final insult dressed up as an honour.
Dignam’s revenge. Sullivan returns home from the grocery store to find Sergeant Dignam waiting in his apartment. Dignam, wearing gloves, says nothing — he simply shoots Sullivan dead and walks out.
The rat. The camera drifts to the balcony, where a rat crawls along the railing with the State House dome behind it. Cut to black.
Who Dies in the Final Sequence?
| Character | How they die | Who kills them |
|---|---|---|
| Billy Costigan | Shot in the head as the elevator opens | Trooper Barrigan, a second Costello mole |
| Trooper Brown | Shot in the same lobby | Trooper Barrigan |
| Trooper Barrigan | Shot after revealing he is a mole | Colin Sullivan, covering his tracks |
| Colin Sullivan | Shot in his own apartment, without a word | Sergeant Dignam |
Why Did Dignam Kill Sullivan?
The film never spells it out, but the likeliest explanation is Madolyn gave Dignam the tapes after Costigan’s death. Dignam knows Sullivan is the rat and that he is responsible for Costigan’s murder — and he does not want an internal-affairs hearing. He wants Sullivan dead. It is revenge, plain and simple — the only justice the film offers, since the official system never catches Sullivan. Alternatively, Dignam may have been working with the FBI, killing Sullivan to bury what the bureau knew. Either way, his silence is the point.
What Does the Rat on the Balcony Mean?
The final shot is Scorsese at his most deliberately on-the-nose. A “rat” is slang for an informant, and this film is crawling with them: Costigan to the mob, Sullivan to the police, Costello to the mob via the FBI. The literal rat on the balcony, framed against the State House, says killing one rat changes nothing. The corruption and the rot are still there, scurrying along the railing long after the men are dead. Some find it too heavy-handed; Scorsese seems to know it, ending a bleak film with a small, grim joke.
The Departed Ending: FAQs
Who kills Billy Costigan at the end of The Departed?
Trooper Barrigan (James Badge Dale) shoots Costigan in the head as the elevator doors open — a second, previously unknown Costello mole inside the police. Sullivan then kills Barrigan and frames him as the only mole.
Why does Sullivan kill Barrigan?
Self-preservation. Barrigan has just murdered Costigan and Brown in front of Sullivan and revealed himself as another Costello informant. Killing him removes the only witness to Sullivan’s treachery — and gives him a scapegoat.
How does Dignam know Sullivan is the rat?
The film implies Madolyn gave Dignam the recordings after Costigan’s death. Dignam was Costigan’s handler and never trusted Sullivan — the tapes confirm what he suspected.
What is the meaning of the rat in the final shot?
It is a visual pun on the film’s central word: everyone is a rat. Costigan informed on the mob, Sullivan on the police, Costello on the mob to the FBI. The rat says the corruption outlives every character.
Does anyone survive The Departed?
Only Dignam and Madolyn are left standing. Costigan, Sullivan, Costello, Queenan, Barrigan and Brown are dead. Madolyn, pregnant and grieving, is the last image of a life that goes on — though the film never says whose child it is.