On October 6, 2006, Martin Scorsese’s crime epic The Departed hit theaters, telling the story of two moles—one embedded in the Massachusetts State Police, the other inside an Irish-American mob—racing to expose each other before their covers are blown. The film ended with shocking violence, with nearly every major character dead and only the true informant left standing. It became Scorsese’s crowning achievement, earning him his first Academy Award for Best Director and winning Best Picture. But the path to that moment began far earlier, with a real-life Boston gangster so dangerous that the FBI protected him for decades, and with a remake of a sleek Hong Kong thriller that few American audiences had ever seen.

The 2002 Hong Kong film Infernal Affairs was minimalist, philosophical, and steeped in Buddhist imagery. It told the story of two men living double lives—one a police mole inside the triads, the other a triad mole inside the police. Scorsese kept the core concept but stripped away the spiritual undertones and replaced them with raw American violence. He moved the story to Boston, swapped Hong Kong triads for Irish-American organized crime, and filled the screen with profanity, paranoia, and blood.

The Hong Kong original ended with ambiguity and hope; Scorsese’s version ended with bullets and betrayal. He didn’t simply borrow a plot. He rebuilt it into a psychological war zone where no one escapes intact. Jack Nicholson’s mob boss Frank Costello was not a purely fictional creation.

He was a ghost of Boston’s most notorious criminal, James “Whitey” Bulger, an Irish-American crime lord who controlled South Boston for decades. Bulger wasn’t just dangerous—he was protected, serving as an FBI informant while running his illegal empire. Scorsese and screenwriter William Monahan studied Bulger’s life closely, pulling from his reputation for extreme violence, his ability to corrupt law enforcement, and his chilling charisma. Nicholson added his own darkness to the role, but the foundation was Bulger, a man who could order executions while having breakfast with federal agents.

Bulger’s real story didn’t end with the movie’s premiere. In 2011, after sixteen years on the run, he was arrested, convicted of multiple serious crimes, and spent the rest of his life in prison. The casting of the film nearly went very differently. Before Leonardo DiCaprio took the role of Billy Costigan, an undercover cop infiltrating Costello’s gang, Tom Cruise was reportedly interested in the part.

Mark Wahlberg wasn’t the first choice for Sergeant Dignam either, but his aggressive intensity transformed the role into one of the film’s most memorable performances. Even Nicholson wasn’t the original pick for Costello; Robert De Niro was discussed early in development, a casting choice that could have echoed their earlier collaboration in Goodfellas. But Nicholson brought an unpredictable chaos that changed everything. Scorsese had a blunt way of describing the world he created.

He called it “moral ground zero. ” There are no heroes in the story, no characters an audience can root for without compromise. Everyone lies, everyone betrays, and everyone is complicit in the corruption that swallows Boston whole. Costigan might seem like the moral center, but he’s willing to destroy his own identity to survive.

Colin Sullivan, the police mole played by Matt Damon, betrays his badge for power and comfort. Even Captain Queenan, who appears honorable, sends a young man into psychological torture without real protection. The film refuses to offer a safe character to believe in, and it refuses to offer redemption. The only reward for doing the right thing is a body bag.

Playing an undercover cop slowly losing his mind required DiCaprio to push himself into dark places. He spent weeks researching how deep-cover operatives handle psychological pressure, studying real cases of agents who cracked under the strain. The panic attacks, paranoia, and identity confusion weren’t just acting—DiCaprio built them into his state during filming. Scorsese encouraged this intensity, often shooting scenes in ways that kept DiCaprio off balance.

Long takes, unpredictable blocking, and Nicholson’s improvised aggression meant DiCaprio never knew exactly what was coming. The rooftop confrontation with Damon was filmed over multiple nights, keeping the tension raw and exhausting. DiCaprio later admitted the role took an emotional toll. His performance shows a man who doesn’t just pretend to be someone else—he forgets who he was.

Damon didn’t just show up and play a cop. He embedded himself with the Massachusetts State Police, learning department protocols, studying how troopers carried themselves, and observing the subtle hierarchies within the force. He also studied real cases of police corruption in Boston, where officers crossed ethical lines, took bribes, and protected criminals. Those stories directly informed Sullivan’s arc—a young cop seduced by power, convinced he could play both sides without consequence.

The result is a character who doesn’t signal his villainy. He blends in perfectly, making him even more dangerous. One of the film’s most chilling visual techniques is subtle enough that most viewers miss it on a first watch. The letter X appears repeatedly just before characters meet their end.

It’s scratched into windows, formed by shadows, built into architecture. Scorsese borrowed the technique from classic gangster films like Scarface. Before Captain Queenan falls to his death, X shapes appear in the building structure. Before other characters face violent conclusions, the camera lingers on crossed beams, taped windows, or intersecting lines.

The X becomes a warning that no one can escape their fate. In a world where everyone is marked for destruction, survival is a temporary illusion. The film’s mirrored structure creates unbearable tension. Two men living double lives, each hunting the other without knowing it.

Costigan infiltrates the mob while pretending to be a criminal; Sullivan infiltrates the police while pretending to be a cop. They’re versions of each other, locked in a deadly game where the first mistake means elimination. Scorsese crosscuts between their parallel investigations, building suspense through near misses and escalating paranoia. The audience knows what the characters don’t, making every interaction feel like a ticking bomb.

Their symmetry isn’t just narrative—it’s existential. Two sides of the same doomed coin. The final image divided audiences immediately. A rat crawling across Sullivan’s window after his sudden demise.

Some called it too obvious, a heavy-handed metaphor. Others argued it was perfect punctuation. Scorsese knew it would be controversial, but he kept it anyway. The rat symbolizes everything the film built toward.

Sullivan was the ultimate informant, the rat who betrayed everyone for personal gain. Ending with that image removes any ambiguity about who he was and what he deserved. But the shot works on another level too: the rat is alive while everyone else is gone. In a film where loyalty and honor lead to destruction, maybe the only survivors are the ones willing to be exactly what they are—rats crawling through the ruins of everyone else’s ideals.

South Boston isn’t just a setting in The Departed. It’s a character that shapes every frame. Scorsese filmed extensively in real neighborhoods, capturing the brick row houses, narrow streets, and working-class bars that define the area. The accents, the tribal loyalty, the Irish Catholic guilt all came from the city’s DNA.

South Boston was Whitey Bulger’s territory, a place where criminal networks and law enforcement had tangled relationships for generations. Damon and Wahlberg, both Boston natives, brought additional authenticity to their roles. Their performances made the film feel less like a crime thriller and more like a documentary of a world that actually existed. Nicholson was given unusual freedom to improvise, and he used it to inject disturbing unpredictability into every scene.

Some of Costello’s most unsettling dialogue was Nicholson’s invention. He even brought props to set without warning. During one scene, Nicholson produced an object that wasn’t in the script, completely catching DiCaprio off guard—his visible discomfort is real. Nicholson understood that Costello needed to feel dangerous, even to the audience.

This creative chaos gave the character an edge that scripted dialogue couldn’t achieve. After The Departed became a box office hit, Warner Brothers approached Scorsese about a sequel. The studio wanted at least one major character to survive so the story could continue. But Scorsese had no interest in extending the narrative.

His vision was about finality. The Departed wasn’t designed to leave room for another chapter—it was built to end in complete annihilation. Keeping someone alive would have undermined the film’s entire message about the cost of deception and corruption. In a world of moral ground zero, there could be no survivors.

The film’s reputation grew stronger with time. Some critics initially compared it unfavorably to Infernal Affairs, arguing that Scorsese’s version lost the original’s philosophical depth in favor of American brutality. Others questioned whether the Academy was finally rewarding Scorsese for his career rather than this specific movie. But two decades later, the film’s themes of surveillance, institutional corruption, and betrayal feel more relevant than ever.

In an era of constant monitoring and eroding trust in authority, the film’s paranoia doesn’t seem exaggerated—it seems prophetic. The question of which identity is real has become a universal experience. Scorsese didn’t just remake a thriller. He built a world where loyalty is a lie, identity is a prison, and survival means becoming exactly what you’re fighting against.

The X marks hidden in every scene, the rat on the windowsill, Jack Nicholson’s unscripted chaos—these details transform a crime film into something that burrows under your skin and stays there.