the departed (2006): Ending Explained

As Ellis Carver, I've long admired Martin Scorsese's ability to peel back the layers of human frailty in his crime epics. The Departed (2006), with its taut screenplay by William Monahan and powerhouse performances from Leonardo DiCaprio, Matt Damon, and Jack Nicholson, stands as a modern masterpiece of moral ambiguity. This "ending explained" dives deep into the film's climactic chaos, unpacking the literal events, their psychological undercurrents, and the broader commentary on identity, loyalty, and betrayal in a corrupt world. If you've just watched the movie or are rewatching it for the umpteenth time, let's explore why this conclusion lingers like a shadow over Boston's rainy streets.

Quick Recap

Set against the gritty backdrop of 1980s South Boston, The Departed weaves a double-sided tale of infiltration and deception. Irish mob boss Frank Costello (Jack Nicholson), a ruthless kingpin loosely inspired by real-life gangster Whitey Bulger, grooms young Colin Sullivan (Matt Damon) as a mole inside the Massachusetts State Police's Special Investigation Unit. Meanwhile, the police, led by the principled Captain Queenan (Martin Sheen) and the abrasive Sergeant Dignam (Mark Wahlberg), recruit Billy Costigan (Leonardo DiCaprio), a troubled academy dropout with family ties to the underworld, to go undercover in Costello's crew. Costigan serves time in prison to build his cover, emerging as a volatile criminal who earns Costello's trust through increasingly brutal acts.

As the years unfold, both Sullivan and Costigan climb the precarious ladders of their false lives. Sullivan rises in the ranks, dating police psychiatrist Madolyn Madden (Vera Farmiga), while Costigan's psyche frays under the strain of isolation, leading him to seek therapy from Madolyn—sparking a clandestine affair. Tensions escalate when both the mob and the police detect moles in their midst: Costello tasks Costigan with rooting out the traitor, while Sullivan's unit hunts for the syndicate's informant. Costigan uncovers a bombshell—Costello himself is a protected FBI informant—sharing this with Queenan. The stage is set for a deadly convergence, where personal loyalties clash with institutional betrayals, forcing each man to confront the hollow core of their divided souls.

What Happens in the Ending

The film's final act erupts in a whirlwind of violence and revelation, compressing the protagonists' fates into a brutal, rain-soaked sequence that feels both inevitable and shocking. It begins with escalating paranoia: after Costigan learns of Costello's FBI ties, he confronts his boss in a tense standoff. Costello, ever the predator, has already eliminated Queenan by throwing him from a rooftop, a cold execution that underscores the mob's reach. Enraged and unmoored, Costigan tracks Costello to an apartment building and shoots him dead in an elevator, ending the tyrant's reign in a spray of blood and echoing gunfire. This act of vengeance marks Costigan's breaking point, blurring the line between his undercover role and his fractured sense of justice.

With Costello gone, the survivors scramble to tie up loose ends. Costigan, now holding evidence of the mob's infiltration (including recordings of Costello's informant status), arranges a discreet meeting with Sullivan at the Massachusetts State House, believing him to be a trusted ally in exposing the corruption. Sullivan arrives, feigning ignorance, and the two exchange tense words in a stairwell—Costigan handing over an envelope that could unravel everything. But betrayal strikes swiftly: one of Sullivan's corrupt colleagues, Detective Barrigan, ambushes Costigan, shooting him execution-style to silence the undercover cop and protect the mole's identity. In a flash of self-preservation, Sullivan then kills Barrigan, staging the scene to frame him as the sole perpetrator. The police arrive, hailing Sullivan as a hero for "taking down the rat." In the aftermath, Sullivan is promoted, walking triumphantly through the halls, but the victory is hollow—Madolyn, pregnant and disillusioned, confronts him about his deceptions before leaving. The film closes on a stark, symbolic image: a rat scurrying across a luxury balcony railing overlooking Boston's harbor, as police sirens wail in the distance.

The Meaning Behind the Ending

At its core, the ending of The Departed is a meditation on the inescapable cycle of betrayal, where no one emerges unscathed from the web of lies they've spun. The literal cascade of deaths—Queenan, Costello, Costigan, and Barrigan—serves as a grim reaper's harvest, illustrating how institutional corruption devours its own. Symbolically, the rat on the balcony is Scorsese's masterstroke, a metaphor for the vermin-like moles (Sullivan and Costigan) infesting both sides of the law. It suggests that treachery isn't confined to the underworld; it's embedded in the system's power structures, much like the real-life FBI scandals that inspired the film. The relentless rain throughout the finale evokes a cleansing that never arrives, washing blood into the streets but leaving moral filth intact.

Thematically, this conclusion probes the psychological toll of duality. Costigan's death, in particular, highlights the tragedy of the "good" infiltrator: his quest for truth costs him everything, underscoring how the system sacrifices its heroes to preserve appearances. Sullivan's survival, meanwhile, indicts the allure of complicity—his promotion is a pyrrhic win, tainted by isolation and the loss of Madolyn, who represents the fragile anchor of authenticity in his life. Scorsese and Monahan use these final moments to comment on societal rot in Boston's Irish-American enclaves, where loyalty is a currency that's always counterfeit, and justice is just another hustle.

Character Arcs and Resolution

The ending crystallizes the arcs of The Departed's central figures, resolving their journeys in ways that expose the moral complexity of their choices. Billy Costigan's transformation from a reluctant recruit to a haunted avenger reaches its zenith in his killing of Costello—a cathartic but fatal assertion of agency. Plagued by identity crises and the weight of his deceptions (exacerbated by his affair with Madolyn), Costigan dies seeking redemption, his arc a poignant reminder of how the undercover life erodes the self. He embodies the film's tragic idealist, loyal to a flawed system that ultimately discards him.

Colin Sullivan's trajectory, conversely, arcs toward chilling ascent. Groomed by Costello from boyhood, he navigates his double life with calculated charm, but the ending reveals the hollowness beneath. Killing Barrigan to cover his tracks cements his corruption, yet his promotion and Madolyn's departure leave him adrift—psychologically isolated, a kingpin in a suit. Madolyn's arc ties their fates together; as the emotional core, her rejection of Sullivan forces him to confront the personal cost of his betrayals, while her bond with Costigan offered a glimpse of genuine connection she can no longer trust. Frank Costello's death resolves his domineering presence, but not before his informant revelation shatters the mob's facade, proving even the boss is expendable. Collectively, these resolutions paint a portrait of characters trapped in a zero-sum game, where survival demands moral compromise.

Alternate Interpretations

While The Departed's ending is relatively straightforward in its literal violence, it invites ambiguities around intent and legacy. One reading posits Sullivan's final promotion as ironic justice: by eliminating Costigan and Barrigan, he inadvertently cleanses the police of overt corruption, allowing the system to perpetuate itself under his subtle influence. Is he truly victorious, or has he become the very monster he infiltrated? Another interpretation views Costigan's death as a deliberate sacrifice—he hands over the evidence knowing the risks, perhaps subconsciously courting his end to escape the torment of his fractured identity. The rat symbol adds layers: it could represent Sullivan as the surviving mole, or a broader indictment of Boston's entrenched crime culture, suggesting the cycle restarts endlessly. These ambiguities stem from the film's refusal to moralize, leaving viewers to ponder if any side truly "wins" in a world of mirrors.

Themes and Symbolism

The ending amplifies The Departed's core themes of identity erosion and the illusion of loyalty, subverting the traditional crime thriller's hero-villain binary. Mirrors and reflections recur throughout the film, but in the finale, they manifest in the characters' final confrontations—Sullivan and Costigan facing off like distorted twins, each seeing their own duplicity in the other. This reinforces the theme of inescapable duality: in a society rife with ethnic loyalties and institutional graft, personal truth becomes the first casualty.

Symbolism abounds in the environmental details—the harbor views and urban decay evoke Boston's divided soul, a city where Irish heritage fuels both community and criminality. The rat, as mentioned, is a potent emblem of infestation, subverting the mob's macho code by equating gangsters and cops to scavenging pests. Thematically, the ending critiques American law enforcement's underbelly, drawing from real FBI-mob entanglements to question who the real "departed" are: not just the dead, but the souls lost to compromise. It reinforces the film's commentary on power's corrupting force, where ambition devours empathy, leaving only echoes of what might have been.

Final Thoughts

Scorsese's ending for The Departed is a triumph of unflinching realism, delivering visceral payoff while inviting endless rumination on the human cost of deception. It works brilliantly because it denies easy catharsis—no triumphant arrests or redemptive speeches—just the cold mechanics of survival in a tainted world. For audiences grappling with today's headlines of institutional betrayal, this conclusion feels prophetically raw, a reminder that in the shadows of power, everyone is playing both sides. If the film's relentless pace left you breathless, revisit these final scenes for their quiet profundity; they elevate The Departed from thriller to tragedy, etching its moral complexities into the canon of American cinema.