- Scene One: The firemen, workers who shovel coal into the engine of a Transatlantic Ocean Liner, are gathered in the forecastle of the ship. They are drinking and joking an hour out of New York City with seven more days aboard. The men are burly and muscular. Yank, the fiercest among them, sits quietly in the foreground. Whenever Yank speaks, the men immediately hush. Yank asks for a beer and the men promptly give him one. As they drink, Yank maintains control as the leader of the group. They joke about thinking, with Yank repeatedly telling them to be quiet because he is trying to "tink." The men mockingly echo him, then erupt into a chorus of "Drink, don't think!" A drunken tenor sings about his lass at home, which infuriates Yank. He orders the tenor to be quiet. Long, quite drunk, makes a Marxist speech, saying their home on the ship is hell and the Upper Class put them there. Yank dismisses him to join the Salvation Army. Paddy, an older fireman, contrasts life on an Ocean Liner with his past on a Clipper Ship, reminiscing about freedom and purpose. Yank tells Paddy he is dead, living in past dreams, and glorifies his own job as the strength of the ship's speed and force.
- Scene Two: Mildred and her Aunt lounge on the promenade deck of the Ocean Liner. They discuss Mildred's need to do service for the poor. Mildred has worked with the poor in Manhattan's Lower East Side and is on her way to Europe for more projects. Her Aunt dismisses this as "slumming" and believes it makes the poor feel poorer. Mildred is waiting for the second engineer to take her to the stokehole. She lied about having permission from her father, the president of Nazareth Steel. The second engineer arrives and escorts Mildred, clad in a white dress, down into the stokehole.
- Scene Three: Yank and the men are hard at work shoveling coal in the noisy stokehole. Yank leads the men. They take a break, but an anonymous whistle-blower overhead commands them to keep working. Yank, enraged, screams at the whistle-blower. Suddenly, he realizes the men have stopped working. Still fuming, Yank turns to see Mildred, who whimpers and faints at the sight of him.
- Scene Four: The men gather again in the stokehold. They replay and mock the scene with Mildred, calling Yank a "filthy beast." Paddy tells Yank Mildred looked at him like a "hairy ape." Infuriated, Yank lunges toward the door to find Mildred but is restrained by the other firemen.
- Scene Five: Yank and Long travel to 5th Avenue in New York City. Long wants to show Yank that all upper-class people are like Mildred. Yank tries to attract attention by bumping into people and accosting a young woman, but only receives polite responses. Finally, Yank is arrested for making a gentleman miss his bus.
- Scene Six: Yank is imprisoned on Blackwell's Island and converses with the other prisoners. They suggest he join the Wobblies or the Industrial Workers of the World to get even with Mildred and her father’s company. Yank realizes he is trapped in a metaphorical cage built by Mildred's father. In a fury, Yank bends the bars of his cell but is restrained by the guards.
- Scene Seven: Yank visits the local I.W.W., but is rejected as they suspect him of being a governmental spy. His radicalism and desire to "belong" make them wary. Yank is thrown out on the street. He spends the night at the Battery and the next morning visits the Monkey House at the Zoo.
- Scene Eight: Yank tries to befriend an ape, believing they are alike—both caged and taunted. He calls the ape his brother and releases it from its cage. However, the ape springs on Yank, crushes him with its massive arms, and tosses him into the cage. Yank dies in the gorilla’s cage.