At a secluded ranch in the New Mexico desert, Angie Lowe (Geraldine Page) and her young son Johnny (Lee Aaker) encounter a mysterious man, known only as Lane (John Wayne), who is quenching his thirst from their river. This stranger, equipped only with a saddle and a rifle, claims to be part Apache and identifies himself as a U.S. Army Cavalry scout who has lost his horse. In exchange for one of her horses, he offers her US Army scrip. Angie explains that her ranch hand has recently left, and she hasn’t yet trained one of her horses for riding. Lane takes it upon himself to tame the horse, impressing young Johnny with his skills.
As dusk descends and a storm sets in, Angie opens her home to Lane, who finds temporary shelter on a floor bed in the corner. While examining him, Angie discovers that his rifle bears the name “Hondo” Lane—a name she associates with notoriety. In a moment of panic, she pulls her pistol and inadvertently fires at him, realizing too late that she had left the gun empty for fear of Johnny's safety.
After Hondo returns to his Cavalry unit, the narrative shifts back to Angie and Johnny, who find themselves in precarious danger as menacing Apaches led by Chief Vittorio (Michael Pate) threaten their homestead. Despite the tension, Angie remains surprisingly calm, recalling their past interactions when the Apaches peacefully watered their horses. Johnny, however, unexpectedly displays courage: he shoots at the approaching Silva (Rodolfo Acosta), breaking his weapon and earning respect from Vittorio, who offers Johnny an Apache name and bonds him as a blood brother. He also ominously hints at the need for a father figure in Johnny's life, suggesting that if her husband does not return, Angie may need to consider an Apache husband.
Meanwhile, in a nearby saloon, Hondo becomes embroiled in a fight that inadvertently connects him back to Angie’s life when he learns that the man he battled, Ed Lowe (Leo Gordon), might be Angie’s missing spouse. Stricken by guilt, Hondo resolves to return her horse. However, danger lurks as Lowe and an ally pursue him for revenge. During a tense encounter with hostile natives, Hondo unexpectedly saves Lowe's life from an Apache attack. Despite their moment of truce, Lowe betrays Hondo out of vengeance for the earlier altercation, resulting in Hondo defending himself and killing Lowe. This grim discovery leads him to find a photograph of Johnny, confirming his relationship to Angie.
As he continues his journey back to Angie's ranch, Hondo encounters yet another Apache group who capture and commence torturing him. A twist of fate occurs when Vittorio, mistaking Hondo for Lowe based on the photo, spares his life after a fierce knife duel with Silva. Hondo's return to the ranch is welcomed under pretense, for when Vittorio questions Angie about Hondo’s identity, she chooses to protect him by lying, stating he is not her husband. Meanwhile, Hondo begins to regain strength, and feelings between him and Angie blossom, creating undeniable emotional tension.
Over time, as the specter of impending war looms, tensions rise further when Lt. McKay (Tom Irish) and his inexperienced cavalry arrive, challenging Angie's way of life. The threat of disclosure regarding Hondo’s actions looms as McKay’s scouts uncover ties between Hondo and Lowe, placing Angie in a precarious position.
Amidst this turmoil, Hondo reveals the truth of her husband’s demise to Angie, who reconciles the secret with her disillusionment towards Lowe. As the army embarks on an operation deeper into Apache territory, Hondo takes a stand, choosing his love for Angie and her son over military loyalty.
The climax unfolds with a fierce Apache counterattack, led by a vengeful Silva, and Hondo shows exceptional leadership as he directs the settlers to defend themselves. In a heart-stopping battle, Hondo confronts Silva, ultimately finding victory at a great personal cost. As he surveys the battlefield's aftermath, Hondo reflects on the impending dissolution of Apache culture, marking a poignant end to a gripping saga of love, bravery, and conflict in a shifting landscape.
