In Waterfront Fists, Steve Costigan finds himself in Honolulu, where Bill O’Brien, a fellow crew member of the Sea Girl, announces that Steve has been matched to fight a formidable opponent from the ship Ruffian that very night. The opponent is rumored to have grown up in the Australian backcountry and is unbeaten aboard his ship. Steve, confident and eager, bets his money on the fight and heads to the Hibernian Bar for some pre-fight drinks, only to end up knocking out a challenging shipmate, Sven Larsen, who had been misled into thinking a victory over Steve would win him a woman’s affection.

Steve then encounters Gloria Flynn, who deceives him into believing she needs Steve to forfeit his fight so her brother can take his place and they can return home to New Jersey. After an attempt to incapacitate Steve fails due to his resilience, Gloria's true motives are revealed: she was hired by Salana and his gang to ensure Tony Andrada from their gym could fight in Steve’s place. However, Steve, overhearing their plan and mistreatment of Gloria, unleashes his fury on the conspirators, saving Gloria and then heading to his fight.

Despite the disorienting experience and physical discomfort from earlier altercations, Steve manages to reach the American Arena in time to face Red Roach, a left-handed fighter with a unique and challenging style. The fight is tough, with Steve struggling against Roach’s unorthodox fighting stance. However, relying on his resilience and fighting spirit, Steve eventually triumphs, knocking out Roach in a dramatic and hard-fought battle.

Following his victory, Steve encounters Gloria once more. She attempts to make amends by claiming a change of heart, influenced by Steve's integrity. Yet, after a deceptive kiss meant to signify her newfound path, she steals Steve's winnings and flees, leaving Steve to reflect on the deceitful nature of his latest romantic encounter and the loss of his prize money.