Sights of Vienna, Austria flash across the screen as the voice of an Englishman narrates the racketeer trade following the turmoil of World War II. He remarks that many unsuspecting amateurs have tried to break into this perilous business, but tragically, they often end up dead. The narrator describes a city split into sectors under the watch of the occupying forces—the English, the Russians, the Americans, and the French—who struggle to keep the criminal elements in check, often even lacking a shared language. As the city lies in devastation, characterized as being "bombed about a bit," he introduces the story of Holly Martins, an American drawn to Vienna by an old friend's promise of work.
Upon his arrival in the city, Holly Martins (Joseph Cotten) steps off the train with anticipation, only to find his friend, Harry Lime, conspicuously absent. After making his way to Lime's flat, he speaks to the building porter (Paul Hörbiger), who struggles with broken English to inform him that he just missed Lime's friends taking away a coffin. With an abrupt finality, the porter informs Holly that Harry has died, hit by a truck right outside the building.
Seeking answers, Martins heads to a vast graveyard and finds himself at Harry's funeral. Nearby, an Englishman (Trevor Howard) quietly informs Holly of who is being laid to rest. Holly scans the gathering and notes two suspicious older men, along with a striking woman (Alida Valli) who seems unaware of his presence. After the funeral rites, Martins walks toward town with the Englishman, who introduces himself as Major Calloway—a police officer representing the British sector in Vienna. Calloway expresses skepticism about Lime's character, deeming him a murderer and a racketeer, which infuriates Holly, leading to a brief scuffle with Sergeant Paine (Bernard Lee), who unfortunately adds to Holly's confusion.
As Holly reluctantly accepts a lift to a nearby hotel, he starts to drink and reminisce about their friendship. It's revealed that Holly is a writer of pulp Westerns, and with Calloway stating firmly that Harry was involved in illicit dealings, Holly vows to uncover the truth behind his friend’s allegations. Recognizing the importance of staying in Vienna, he agrees to speak at a lecture hosted by Crabbin (Wilfrid Hyde-White), an Englishman excited to meet a writer, believing his insights could promote British cultural propaganda.
While settling into his hotel, Holly receives a phone call from a man claiming to be Baron Kurtz (Ernst Deutsch), a supposed friend of Harry’s. Their subsequent rendezvous unveils mysteries surrounding Harry’s demise; Kurtz recounts the events of that fateful day. As they piece together the scenario, the involvement of another character, Popescu, is reluctantly revealed. Holly's investigative pursuits lead him to Anna Schmidt, the actress who was romantically linked with Harry. Their interactions expose her deep sorrow and the intricate web of Harry's life that Holly begins to unravel.
As Holly confronts various witnesses, including the porter and the doctor (Erich Ponto), he discovers inconsistencies in their stories, deepening his suspicions surrounding Harry's untimely death. Anna becomes an ally in his quest, fraught with tension as they probe deeper into the foggy circumstances of Harry’s final moments. However, their investigations take a dark turn when they learn of the threats that hover over them.
With mounting dread, Holly realizes that avoidance is no longer an option, especially as he evades pursuers who believe him responsible for the porter's murder. In a gripping turn of events, Holly attends a lecture meant to display his literary talents while being shadowed by dangerous figures. Encounters with characters like Popescu and Calloway lead him to numerous truths about Harry’s dark undertakings, forcing him to grapple with the moral collapse of his friend, who had profited from the suffering of innocents through dilapidated medical supplies.
Yet, amidst these revelations, Holly's resolve begins to wane as he struggles with loyalty to a friend whose morality has crumbled and the undeniable pull of justice. The climax reaches a nerve-racking moment in the sewers of Vienna, where Holly must confront Harry, who, in a state of desperation and dismay, attempts to escape the tightening noose of law and betrayal.
> "You can't take sides against the law! You will be made to suffer!"
In the resulting confrontation, Holly is left confronted by the grotesque realities of friendship and betrayal, leading to a heartbreaking conclusion that echoes the tragic loss of camaraderie amidst moral decay. After the fallout, Holly finds himself back at another funeral, standing alone among the disillusioned remains of whatever idealism he once had, grappling with his own feelings as he observes Anna walking past him without acknowledgment.
Through this tale, we not only witness a gripping mystery but also the unraveling of the human condition, mirrored in Holly’s harrowing journey through the labyrinth of Vienna, where friendship, betrayal, and the haunting specter of the past intertwine to create a spellbinding narrative that lingers well beyond its final frames.
