The story begins with Steve Costigan performing a handspring in the American Bar, celebrating his return to Port Arthur on shore leave from the ship, the Sea Girl. His celebration is cut short when he accidentally crashes into a table occupied by the Sea Girl’s captain, leading to a heated exchange. The captain reveals that the Sea Girl is about to be lost due to his inability to pay off a debt. This news shocks Costigan, who had no idea the captain was in such dire straits.

Moved by the captain's plight, Costigan decides to raise the money needed to save the Sea Girl. He concocts a plan to fight in a boxing match against Shifty Strozza, a middleweight contender, with the intention of using the prize money to pay off the captain's debt. However, when Strozza dismisses Costigan's request for help, Costigan knocks him out and takes his place in a boxing event at Jim Barlow’s Wharfside Arena.

Despite suffering a broken arm, Costigan fights three tough opponents one after another in a grueling series of matches. He uses a combination of boxing, resilience, and sheer force of will to defeat each opponent. In a dramatic finale, Costigan, barely conscious and severely injured, defeats the final opponent, Bill Brand, winning the prize money.

After the fight, Costigan, now heavily bandaged and in pain, goes directly to the bar where he expects to find the captain. Without seeking acknowledgment or thanks, he gives the captain the money to save the Sea Girl. The captain, moved by Costigan's selfless action, expresses his gratitude, acknowledging the deep bond and respect between them. The story ends with a moment of reconciliation and mutual respect, highlighting the theme of hard-fisted sentimentality that defines the lives of these rugged men.