Floyd Hilston, a clown at Owen Gillman's circus, is devoted to "Fearless Fagan," a lion he has raised since Fagan was four days old. Through Floyd's gentle care, Fagan behaves more like a pet than a wild animal, much to the chagrin of lion tamer Emil Tauchnitz, who beratees Floyd for his naïvité. One day, Gann, an FBI agent, comes to the circus to arrest Floyd for draft-dodging, but sympathetically gives him a day to enlist when he realizes that the circus moved around too much for Floyd to receive his notice. Floyd is happy to serve his country, but worried about Fagan, refuses to let him stay with the circus, and Emil. Having no luck in finding the perfect home, Floyd sneaks Fagan into the woods on Fort Ord, when Floyd must report. Each day Floyd sneaks off to romp with Fagan and play his favorite song on the phonograph, but the rest of Fagan's time is spent in Floyd's van. At formation one morning, Sgt. Kellwin reads a statement that the Army is initiating a new policy to try to make servicemen happy, and tells the men to come to him with their problems. After dozens of soldiers give phony excuses for receiving leaves, Kellwin is disgusted and thinks that Floyd's explanation of needing time to look for a home for his pet lion is just another ruse. A few days later, while Floyd is paying his daily visit to Fagan, Abby Ames, a singer who is coming to entertain on the base, stalls her car near the van. Hearing music, Abby goes to investigate. She is frightened of Fagan, but Floyd, who recognizes her from posters, assures her that he is harmless and asks her not to tell anyone about seeing him. That night, after breaking her promise, Abby accompanies company commander Col. Horne and several soldiers to find Fagan. When they cannot locate him, Horne accuses Abby of orchestrating a publicity stunt. To prove Horne wrong, Abby tells him that "the soldier," whose name she does not know, has promised to come to her dressing room after the show. When Floyd shows up, he is arrested, but after he honestly reveals what happened, and Kellwin comes forward to say that Floyd had tried to enlist his aid, Horne decides to help. Horne then assigns Kellwin the job of finding a good home for Fagan. Kellwin has no success, until Abby, who has softened toward the affable Floyd, suggests that they try publicity. With the help of photos of the pair participating in various activities, their story becomes front page news and a nearby farm family, the Ardleys, offers to take Fagan. After saying his goodbyes to the lion, Floyd tells Abby that he loves her and is making her beneficiary of his Army life insurance, as well as Fagan's guardian, in case anything happens to him. Though she still thinks Fagan is masking his true nature, she is touched and agrees. Some time later, the company goes on night maneuvers. Meanwhile, the lonely Fagan paces his cage and opens the latch, just as he used to do in the circus act. He ambles onto the base, where he terrifies a barracks of WACS when he casually walks to the radio to listen to his favorite song, "The Loveliest Night of the Year." Fagan then wanders out into the woods and frightens Kellwin and some other soldiers. When Floyd is told to make contact with Kellwin on the walkie talkie, Fagan, recognizing Floyd's voice, cuddles the device. Kellwin, who is hanging from a tree, screams that the lion is there, and Floyd and Capt. Daniels rush to the rescue. The next day, when the Ardleys tell Horne that they can no longer keep Fagan, the colonel has no other choice than to tell Floyd that he must either let Gillman have the animal until his enlistment is up, or chloroform Fagan. Although he still fears that Gillman will enable Emil to mistreat Fagan, Floyd agrees to place him with the circus. Rather than let Fagan go, Floyd decides to go AWOL and puts him into the van. He is stopped only by Abby, who does not want him to get in serious trouble, and blocks the van with her car. As they argue, Gillman and Emil arrive and Emil takes charge of Fagan. Emil's rough treatment frightens, then angers Fagan, and he attacks Emil. Floyd fails to soothe Fagan by playing circus music, but Kellwin and some soldiers arrive in time to save Emil. He has been mauled, and has hurt Fagan's mouth during the attack and the lion runs off. Realizing that the wound will turn Fagan into a killer, Floyd asks for Emil's gun and goes after Fagan. Abby follows closely behind and begs Floyd to shoot when they find Fagan, but Floyd cannot. Fagan then attacks Floyd's leg, but despite his intense pain, Floyd gently calms Fagan down. Abby then runs to get the van and manages to lure the animal into his cage with soothing words and his toy duck. The next day, Kellwin visits Floyd in the hospital and assures him that his leg will be fine and that Emil is not badly hurt. He also says that Horne has arranged for him to have the soldier's medal and a ten-day pass to visit Abby and Fagan in Hollywood. After Floyd has recuperated, he goes to Abby's house and is shown into the living room by her maid. When he sees a lion skin rug on the floor, he is aghast, until Abby takes him outside and shows him that Fagan is happily taking a swim in her pool.
