A naval officer longing for active duty clashes with his vainglorious captain.

In April 1945, Lt. (j.g.) Douglas A. Roberts is a cargo officer on board the Reluctant , a Navy supply ship called the "Bucket" by its crew. Harbored near a South Pacific island that is far from the fighting, the crew suffers from intense heat, boredom and a tyrannical captain, who takes sadistic pleasure in undermining their morale. Roberts intervenes on the crew's behalf as much as possible. Watching him butt heads with the captain lifts the crew's spirits and provides almost their sole entertainment. However, Roberts, who quit medical school to fight the war, feels completely wasted aboard the "Bucket." Alone on watch one night, Roberts watches a convoy of fighting ships sail by and the next morning confides to Doc, the medical officer and his closest friend aboard ship, how much he aches to join them. Although Doc tries to convince him that standing up for the crew against the bullying captain is a valuable service, Roberts remains discontent. As a weekly ritual, Roberts writes the Navy Department to request a transfer to active combat, but his request is systematically vetoed by the captain, whose signature is required for approval. The captain, an uncouth ex-Merchant Marine, is threatened by Roberts' superior education and intelligence and the admiration given him by the crew. However, he expects that Roberts' hard work will help him get promoted. It has already won the captain an award for "superior cargo transfer," a palm tree that he displays proudly outside his cabin. For over a year, the captain has refused to approve leave and he frequently takes away movie nights and other small privileges. When the sailors discover that binoculars provide them with a clear view of the nurses's shower room in a hospital on the nearby coast, they experience their first release from drudgery in over a year. The ship's morale officer, young ensign Frank Thurlowe Pulver, who is also in charge of the ship's laundry, shares Roberts' quarters. Womanizer Pulver is also aware of the nurses, and finagles a trip to the hospital to pick up aspirin for Doc. While there, he convinces head nurse, Lt. Ann Girard, to come to the ship later by promising to share a bottle of scotch with her. Back on board, while preparing his bunk for seduction, Pulver is distressed to learn that Roberts, the owner of the scotch, has used it to bribe an official to send the Reluctant to a liberty port. Amused by Pulver's panic, Roberts and Doc mix up simulated scotch, called "jungle juice," from alcohol, Coca-Cola, iodine and hair tonic. Although Roberts admits that Pulver is "thoroughly likable," he accuses him of being, among other things, disorganized, and challenges him to finish one thing that he starts. As an example, he suggests that he carry out his idea of putting marbles in the captain's overhead. However, Pulver's fear of the captain renders him incapable of defiance. When Ann appears with the other nurses in tow, Pulver despairs of getting her alone. With Roberts' permission, Pulver pretends to be the ship's cargo officer. While he shows them around, the nurses, who are undeceived by his pretensions, discover the sailors' view of their quarters and leave immediately to hang curtains. When the Reluctant sails to the liberty port, the captain, who learns about Roberts' bribe, forbids the men to go ashore. Arguing that the men are "breakable," Roberts begs him to relent, finally winning the crew one night of shore leave at great personal cost: In return, he must cease questioning the captain's orders, especially in front of the men, and give up writing transfer applications. During their night onshore, the men, unaware of Roberts' concessions, unleash all their pent-up energy. They crash an Army dance, fight with soldiers, terrorize women, steal an admiral's goat and mistake the French Colonial governor's mansion for a bordello. Roberts hopes the night will give them strength for the "miserable, endless days ahead of them." The next day, the ship is banished from the port. The captain, livid at the blemish on his record, forces Roberts, in front of the crew, to assist in their punishment. Confused by Roberts' sullen compliance, the men are further mystified when he stops writing transfer requests, and his growing irritability makes them wonder if he is "bucking for a promotion." Later, upon hearing that Germany has surrendered, Roberts puts one of the crewmen, Dolan, on record for a minor infraction, and then, near tears, begs Doc to give him a medical transfer. Guessing that Roberts is suppressing resentment because he made an agreement on the men's behalf, Doc refuses and tells the concerned Pulver afterward that Roberts is panicking because the war is ending before he can join it. Trying to cheer Roberts, Pulver builds an explosive out of a toilet paper roll and some fulminator mercury, which he promises to throw under the captain's bunk. When Roberts laughs hysterically at the idea, he goes to the laundry room to test it. After an explosion, soapsuds flood the ship, and Pulver returns to say that his whole supply of mercury blew up by accident. The rebellion ends after the captain is told that a steam pipe broke. That night, Roberts apologizes to Dolan, but he and the other men respond coldly. Left alone on deck, Roberts listens to the radio broadcast of a speech that urges the free world to stand up to stupidity and arrogance. Inspired, he throws the palm tree overboard, then goes to bed. During the night, the captain, seeing the palm missing, sounds a general alarm. The men, at first believing they are under attack, scurry to find their battle stations and from there watch the ensuing "showdown." The captain, forgetting to turn off the p.a. system, accuses Roberts of breaking his promise and the men then realize that Roberts bought their night of liberty. Roberts remains calm in the face of the captain's spewing anger, and summons Doc when the captain almost passes out. The eavesdropping men thoroughly enjoy the drama of the night and when Roberts emerges from the cabin, their admiration is obvious. Weeks later, Roberts receives orders to transfer to a destroyer stationed in Okinawa, which surprises him, as he has not requested a transfer in months. While packing, he mentions to Doc that, as far as the men are concerned, he is easily replaceable. Doc, however, confides a secret: The men forged a transfer request and then forged the captain's signature of approval, to show their gratitude to Roberts for getting them shore leave. Before he leaves, the men toast Roberts with "jungle juice" dispensed from a fire extinguisher and present him with a handmade medal shaped like a palm tree and inscribed, "Order of the Palm, for action against the enemy above and beyond the call of duty." Deeply moved, Roberts puts on the medal, salutes and leaves. Some time later, the captain orders a 24-hour watch on a palm tree he has dug up to replace his prized one. Pulver, who has been assigned Roberts' position, frets over confronting the captain about showing a movie to the men. At mail call, Pulver receives from Roberts a letter written three weeks earlier. Having gained perspective from his new post, Roberts writes philosophically about the courage the Reluctant men showed while surviving monotony. Although Roberts is now where he needs to be, he is proud to have served with them and treasures their medal more than a Congressional Medal of Honor. A second letter Pulver receives, which was written by a friend serving on Roberts' ship, reports that Roberts was killed by a Japanese suicide bomber while drinking coffee in the ship's wardroom. The men mourn, but Pulver, emboldened by shock, throws the captain's palm tree overboard, pounds on his cabin door and belligerently demands, "Now what's all this crud about no movie tonight?"