The Show is set on a South Pacific island during World War II. It opens with two Polynesian children, NGANA and JEROME, singing a charming French song. They are the children of EMILE de BECQUE, a French plantation owner. Ensign NELLIE FORBUSH, from Arkansas, a nurse in the US navy, falls in love with EMILE and his way of life on his plantation. Both wonder if the other reciprocates their feelings ("Twin Soliloquies"). EMILE recalls how they met at a dinner given at the officers' club ("Some Enchanted Evening") and were immediately drawn to each other. NELLIE is not aware at this point that NGANA and JEROME are EMILE'S children.

Meanwhile, the restless sailors, led by LUTHER BILLIS, lament the absence of women. BLOODY MARY, a Tonkinese (Vietnamese) grass-skirt seller from the island of Bali Ha'i joins the men and tries to sell her wares. BILLIS and the sailors proclaim that, "There is Nothin' Like a Dame". Lieutenant JOE CABLE, a US Marine, arrives on the island to take part in a dangerous spy mission that might help turn the tide of the war against Japan. BLOODY MARY tries to convince him that "Bali Ha'i" is his special island.

NELLIE decides she knows very little about EMILE and tells the other nurses that she's going to "Wash That Man Right Outa My Hair" and break up with EMILE. However, she really does love him and when he invites her to a party to meet all his friends, NELLIE eagerly accepts.

BILLIS convinces Lt. CABLE to accompany him to Bali Ha'i. where BLOODY MARY introduces CABLE to her teenage daughter, LIAT. The two fall in love, just as BLOODY MARY planned. NELLIE and EMILE by this time are gaining deep affection for each other, but, when EMILE tells NELLIE that the children are his and that he is a widow, she changes her mind. LIAT and CABLE spend more time together and MARY urges them to get married and talk "Happy Talk" all day long. CABLE says he cannot marry LIAT. His refusal infuriates MARY.

NELLIE is responsible for the Thanksgiving Show for all the sailors, and she does a Vaudeville turn dressed as a sailor singing the praises of his "Honey Bun". BILLIS plays Honey Bun.

Dejected and with nothing to lose, EMILE agrees to join CABLE on his dangerous mission behind Japanese lines. The two send back reports on enemy forces which the Americans use to intercept and destroy Japanese convoys. "Operation Alligator" gets underway, and the previously idle sailors, including the reluctant LUTHER BILLIS, go off to battle. CABLE is killed; EMILE narrowly escapes a similar fate. NELLIE, meanwhile, spends time with NGANA and JEROME. EMILE returns home to NELLIE and his - soon to be their - children.