THE curtain rises on an island in the Pacific during the Second World War. At the home of the wealthy, middle-aged French planter, Emile de Becque, two Eurasian children are performing an impromptu minuet and chanting a French ditty ("Dites-moi"). Emile, who had settled on this island some years before the outbreak of the war, is host at dinner to the charming American nurse, Ensign Nellie Forbush. She reveals to him some facets of her personality ("Cockeyed Optimist"). The two are strongly attracted to each other, and it does not take them long to realize that they are in love ("Some Enchanted Evening"). Before Nellie leaves, Emile asks her to consider becoming his wife.

 In another part of the island a group of American sailors, Seabees and Marines are singing the praises of Bloody Mary, a Tonkinese ("Bloody Mary is the Girl I Love"). Bloody Mary excites the interest of the Americans in the mysterious nearby island of Bali Ha'i, declared off-limits to them; the Americans suspect that the French planters have secreted there all their womenfolk as protection from the Americans. All this talk reminds the Americans that they have everything on this island that they could possibly want except--dames. They lament the lack in no uncertain terms ("There is Nothing Like a Dame"). When the handsome Lieutenant Cable appears, Bloody Mary instantly sees in him a prospect as a husband for her lovely daughter, Liat. Mary now begins to stimulate also Cable's interest in Bali Ha'i ("Bali Ha'i"). While his curiosity in the place is aroused, there are for the moment more important things on Cable's mind: he is to establish a coast watch on a nearby Japanese-held island. Since Emile de Becque knows this terrain well, Cable wants to induce him to join him on this dangerous mission. The commanding officers, consequently, call on Nellie's help by asking her to find out as much as she can about Emile. Meanwhile, Nellie has come to the conclusion that marriage with Emile might very well be a mistake, considering the differences in their age and background ("I'm Gonna Wash That Man Right Outa My Hair"). But Emile succeeds, at last, in convincing her that all her fears are groundless. There is no longer any question with Nellie that she loves Emile more than any man she has ever met ("I'm in Love with a Wonderful Guy").

 Having found the woman of his dreams, Emile has no intention of endangering his life by helping Cable; and no arguments can persuade him to change his mind. The mission temporarily delayed, Cable can now devote a few days for recreation. He makes for Bali Ha'i, where Mary brings him to Liat, a sensitive Tonkinese girl of seventeen. Though she speaks only French and Cable only English, they fall helplessly in love. Cable takes Liat in his arms and tells her of his feelings in song ("Younger than Springtime").

 Back at Emile's plantation, Nellie discovers for the first time that he is the father of two Eurasian children, having formerly lived with a Polynesian girl. This news so upsets Nellie that she leaves Emile, determined never again to see him.

 Bloody Mary brings Liat from Bali Ha'i to convince Cable to marry her. She describes the happy life he would have with the girl, a life full of the most beautiful things ("Happy Talk"). Bloody Mary is even willing to turn over to Cable all the money she has saved. Cable is so deeply moved by all this that he presents Liat with a gift of a man's gold watch which he had inherited from his grandfather. Tenderly, pathetically, Cable tries to explain to Mary that he can never marry Liat. In a fit of temper, Bloody Mary smashes the watch on the ground, drags Liat away and mumbles that she will arrange to have Liat marry somebody else.

 Emile now comes to Nellie to plead with her not to allow his Eurasian children to come between them. Nellie insists that it is not the children that bother her, but their mother; the thought of Emile having loved a Polynesian is too much for her to bear. Cable, a witness to this conversation--and who instantly recognizes that he too rejected love because of racial prejudice--comments softly that hate is not born to man, as Nellie is tempted to believe, that it happens after birth; that a man has to be taught to hate and fear ("Carefully Taught"). He then tells Emile that should he survive this war he, too, would like to make his permanent home on this island. But the island has suddenly lost all its appeal for Emile, now that he has lost the woman he loved and with her his paradise ("This Nearly Was Mine"). In fact, since he has no use for life any longer, he is ready to accompany Cable on their dangerous war mission.

They penetrate the Japanese island, whence they relay back information which makes it possible for the American forces to destroy twenty Japanese surface crafts and pave the way for a successful invasion of fourteen Japanese-held islands. In the performance of his duties Cable is killed. But Emile survives. When he returns to his plantation he finds Nellie waiting for him--playing with and feeding his children.