Harry Fabian, an ambitious American tout and con man, is maneuvering his way through the gritty underbelly of London. He finds himself entangled in a fractured relationship with the honest Mary Bristol, as well as with nightclub owner and businessman Phil Nosseross and his cunning wife, Helen.
While attempting to perpetrate a con at a wrestling match, Fabian witnesses a heated argument between Gregorius, a seasoned Greek wrestler, and his son Kristo, the organizer of the event who holds sway over London’s wrestling scene. Gregorius passionately criticizes Kristo's promotion for being "tasteless exhibitionism" that tarnishes the noble Graeco-Roman traditions of wrestling, before departing with Nikolas, a fellow wrestler.
Seeing an opportunity, Fabian befriends Gregorius, believing that with the support of Kristo's father, he could successfully stage wrestling bouts in London without interference. He approaches Phil Nosseross and Helen with his ambitious proposal, seeking an investment. Initially doubting him, Nosseross, at his wife's coaxing, offers to match half the £400 Fabian needs, thus stretching Fabian's desperation to its limits.
In a bid to gather the necessary funds, Fabian approaches a series of untrustworthy allies: Figler, an unofficial head of a community of beggars, Googin the forger, and Anna, a Thames smuggler, but to no avail. It is then that Helen offers to lend him the £200 he needs, having sold an expensive fur coat gifted by her husband, in exchange for securing a license to keep running her nightclub. In a twist of deception, Fabian tricks her into believing he can procure the license via a forged document crafted by Googin.
As the plot thickens, Nosseross receives a warning from Kristo's associates to steer clear of Fabian, but in his suspicion toward Helen, he fails to pass on the warning. Undeterred, Fabian proceeds to launch his own wrestling gym with Gregorius and Nikolas, enlisting Nosseross as a silent partner.
Tensions escalate when Kristo discovers his father’s support of Fabian’s venture and conspires with Nosseross to eliminate him. In an effort to drive a wedge between Gregorius and Fabian, Nosseross withdraws his backing and cunningly suggests that Fabian pit Nikolas against The Strangler, an extravagant wrestler favored by Kristo.
In a dangerous game of manipulation, Fabian persuades Mickey Beer, The Strangler's manager, to agree to the fight, all while taunting The Strangler into confronting Gregorius. Gregorius, convinced that the match will validate his traditional wrestling style, accepts. When Beer demands £200 for his services, Fabian turns again to Nosseross for the cash, but instead, Nosseross informs Kristo of The Strangler’s presence in Fabian's gym.
Betrayed and desperate, Fabian steals money from Mary and rushes back to the gym. However, during the intense showdown, The Strangler provokes Gregorius, leading to a brutal bout where Nikolas suffers a broken wrist. Gregorius ultimately prevails but tragically collapses shortly after from exhaustion, dying in his son’s arms.
Heartbroken and realizing he has no business and nowhere to turn, Fabian flees. In his misguided quest for revenge, Kristo places a £1,000 bounty on Fabian, igniting a manhunt across London. As the night unfolds, figures from the city's underworld pursue him, and Figler attempts to claim the reward but fails to capture him.
Meanwhile, believing she has secured her future, Helen discovers her license is merely a forgery, prompting a desperate return to Nosseross, only to find he has taken his own life in despair over her absence.
With nowhere left to hide, Fabian seeks refuge at Anna's houseboat on the Thames. Just as Kristo closes in on him, Mary arrives, and in a moment of twisted sacrifice, Fabian shouts to Kristo that Mary betrayed him, hoping to allow her to collect the reward money for his arrest. As he rushes toward Kristo on Hammersmith Bridge, he's ultimately confronted and slain by The Strangler, who discards his body into the river. The Strangler is quickly apprehended, leaving Kristo to walk away, while Mary finds solace in the company of her neighbor and friend, Adam Dunne, who harbors unspoken feelings for her.
