The Hairy Ape tells the story of the fall of Yank, a proud and powerful stoker working aboard a steamship. Though respected by his fellow workers, a chance encounter with a millionaire's daughter who disdains him as an "ape" leads to a vain quest for vengeance and the breakdown of his personality, leading eventually to a confrontation with a real gorilla who kills him.
O'Neill based the play in part on a real man, an Irish sailor named Driscoll, whom he roomed with in New York. O'Neill had been terribly impressed by the gruff older man's confident and manly view of life and was duly shocked to hear some years later that Driscoll had committed suicide by jumping from a ship. The play at once represents a personal attempt to come to terms with this suicide and the playwright's finding in the drama of the demise of a manual laborer an essential story of humanity in modern society.