To an untidy little country saloon on a wild coast of Mayo, in Ireland, there comes a shy, frightened youth, Christy Mayo, with a tale of having killed his cruel father, with a single blow of a spade, a week ago on a distant farm. He is fleeing the police, and is accepted by Michael James, the publican, and his pretty but tart-tongued daughter, Pegeen, as a hero whom it would be well to hire as pot-boy.
So Christy stays on, and Michael James and his cronies leave for a wake. Pegeen scornfully dismisses Shawn Keogh, her betrothed, a young farmer who fears to stay alone with her until dispensation for their wedding is granted, and Christy tells her--the first woman to allow him a confidential talk--that he has been a cloddish young farmer, shy and unheeded by the girls. But now his ego is inflated at her attention and at the realization that he is, indeed, a sinister figure.
Their chat is interrupted by the Widow Quin, a forthright woman of thirty, who has come, at Shawn's urging, to take Christy to her house to lodge. She tells Christy that he and she will be great company, and he asks if she, too, killed her father. Pegeen scornfully declares that it was a sneaky kind of murder--she hit him with a rusty pick and he died of blood poisoning. The women debate sharply for possession of the thrilling stranger, but Christy elects to stay where he is. He goes to sleep wondering, in his new-found importance, why he didn't kill his father long ago.
Next morning, while Pegeen is out, the Widow Quin is prompt to return, announcing that she has entered him to compete in the sports of that afternoon. Shawn, Pegeen's betrothed, is a visitor also; he offers Christy the half of a ticket to the Western States, his new hat, his breeches with the double seat and his new coat if Christy will leave Pegeen to him. While Christy is trying on the fine clothes, the Widow Quin makes a deal of her own to help Shawn, promising to wed Christy herself in return for a red cow and other tribute.
But Christy, swaggering in Shawn's finery, sees no reason why so rich a field should be abandoned by "a gallant orphan cleft his father with one blow to the breeches belt." He opens the door to seek Pegeen, but staggers back and cries that the ghost of his father is approaching. He hides behind a door. In comes Old Mahon, a squatter with bandaged head, seeking his son. The Widow, enjoying her role, quizzes him, and is promptly told that Christy is a lazy lout, "making mugs at his own self in a bit of glass," a weakling who can neither drink nor smoke and is terrified by girls.
The Widow sends Old Mahon off on a false clue, then jeers at the crestfallen Christy: "Well, you're the walking Playboy of the Western World, and that's the poor man you had divided to his breeches belt!" She assures him that Pegeen will knock his head and drive him off as a liar, and suggests that he would do well to marry her. But Christy determines that he will win Pegeen, promising the Widow a share when he is master of the saloon if she will aid him. She agrees, and Christy runs out to take part in the sports and make a name for himself.
While he is gone, however, Old Mahon returns to the saloon to boast of his cracked head, and the Widow is hard put, despite canny lies, to make him appear a madman and not Christy's father. She can see from the window that Christy is performing heroic feats in the races and games, and she finally induces Old Mahon to believe that he is "a sniggering maniac" and had better escape--that his shy son could not possibly be this champion Playboy of the Western World. Old Mahon slips out. One farmer is suspicious and follows to talk further with him.
Christy, escorted by a cheering throng, returns triumphantly to the house with his prizes. He now calls for the greatest prize of all, Pegeen's promise to marry him. Pegeen fears that he will return to some girl in his own town, but the now eloquent Christy protests: "I will not, then, and when the air is warming in four months, or five, it's then yourself and me should be pacing Neifin in the dews of night, the times sweet smells do be rising, and you'd see a shiny new moon, maybe, sinking in the hills." He goes on to picture the delights of a poacher's life, but cools when Pegeen agrees; he concedes that, after all, her own snug home would be best.
Michael James returns from the wake, drunk, to interrupt with the announcement that dispensations have come for the wedding of Pegeen and Shawn. The latter has accompanied him with the news. Pegeen declares that it is Christy she will wed, and Michael James eggs the young farmer to fight. Shawn flies out the door when Christy picks up a significant spade.
Michael James has overcome his drunkenness enough to give Christy and Pegeen his blessing when there is a shout, and Old Mahon rushes in, followed by the Widow Quin and a curious crowd. Old Mahon knocks Christy down and begins to beat him. Pegeen rushes to her lover's rescue, but learns that the attacker is his father who, indeed, has not risen from the dead. "Do you think I look so easy quenched with the tap of a loy?" he bellows. She turns on Christy: "And it's lies you told, letting on you had him slitted, and you nothing at all!... And to think of the coaxing glory we have given him and he after doing nothing but hitting a soft blow and chasing northward in a sweat of fear!"
Christy can find no comfort in the lies of the now exhausted Widow Quin, or in the jeering crowd, and he again is pale with terror as Old Mahon heaps humiliation upon him. A girl in the crowd suggests maliciously that he ask Pegeen to help him, but he says: "I will not, then, for there's torment in the splendor of her like, and she a girl any moon of midnight would take pride to meet.... But what did I want crawling forward to scorch my understanding at her flaming brow?" The weeping Pegeen tells Mahon to take him off or she will have him beaten.
Her scorn revives Christy, the champion. As Old Mahon bullies him to come, he seizes a spade and pursues his father into the yard--from whence there comes a yell, then silence. Christy returns, half dazed, and the Widow Quin begs him to run or he will be hanged. But he will not go. He says: "What good'd be my lifetime, if I left Pegeen?... Leave me go ... when I'm thinking of my luck today, for she will wed me surely, and I a proven hero in the end of all."
The men report Old Mahon doubly dead, and Pegeen herself slips a noose over the dazed Christy's arms. He asks what she has now to say to him, but Pegeen replies: "A strange man is a marvel, with his mighty talk; but what's a squabble in your back-yard, and the bloy of a loy, have taught me that there's a great gap between a gallous story and a dirty deed." He begs her to free him, to return no more, but Pegeen is merciless; she says that she and her neighbors might hang for his deed.
Christy, having managed to bite Shawn in the leg, is forecasting his dramatic execution before weeping fine ladies when Old Mahon crawls in. He loosens Christy and respectfully bids him to come on and leave the fools of Mayo. And Christy, the proved "master of all fights from now on," grandly orders the old man to lead. "The thousand blessings upon all that's here," he says, "for you've turned me a likely gaffer in the end of all, the way I'll go romancing through a romping lifetime...."
As he leaves, Shawn suggests that their wedding can now go on, but Pegeen cuffs his ear and sends him off. She covers her head with her shawl and loudly laments: "Oh, my grief, I've lost him surely! I've lost the only Playboy of the Western World!"