Outlaws Robert Hightower (John Wayne), Pedro "Pete" (Pedro Armendáriz), and William "The Abilene Kid" (Harry Carey Jr.) are planning to execute a bank heist. They begin their journey by filling their canteens and a water bag at a spring, eventually reaching a town in Arizona named Welcome. During their stop at the home of Perly "Buck" Sweet (Ward Bond), they enjoy coffee made by his wife, Mae (Mae Marsh). As they converse, the couple inquires about a wagon that is presumed lost, heading from New Jerusalem. Offering directions to the local bank, the situation becomes tense when they notice Buck's badge as he readies himself, prompting the outlaws to leave cautiously but still intent on robbing the bank.
After successfully stealing the money, their escape takes a turn as lawmen burst out of their office, shooting William off his horse. With quick thinking, Robert manages to hoist William onto his own horse, and they flee. Buck, relentless in his pursuit, takes to the desert, where he shoots their water bag without them realizing it. As their resources dwindle, the group aims for a water tower known as Mojave Tanks, but Buck has foreseen their move and positioned his deputies strategically at nearby water towers to trap them.
In a moment of desperation, Robert decides they must turn back toward the Terrapin Tanks situated to the north. However, fate intervenes when a fierce sandstorm strikes, leading to the loss of their horses. When they finally arrive at the tanks, Robert discovers an abandoned wagon containing a pregnant woman on the brink of childbirth. Her husband has been absent, pursuing their thirsty horses and leaving her in dire straits. The tanks, unfortunately, are dry, having been sabotaged with dynamite by the husband, unable to dig down to find the water.
In a brave act, Robert urges Pedro, who has past experience as a family man, to assist the woman with her delivery. As Pedro steps in to help, Robert and William begins to gather whatever water they can from barrel cactus heads. The woman successfully gives birth and expresses her gratitude to them, requesting that they become godfathers to her son, whom she names Robert William Pedro Hightower after them. Tragically, she passes away shortly after, but her request instills a deep sense of responsibility in the men as they undertake to care for the newborn.
Removing her remains, they search the wagon and find a book on infant care, along with baby clothes, canned milk, and a Bible. As days pass and supplies diminish, they set out into the relentless desert in search of New Jerusalem, carrying the baby with them. Meanwhile, Buck, growing impatient at Apache Wells, deduces that the outlaws must have moved to Terrapin Tanks and shifts his efforts accordingly. When he finds the empty wagon and the clothing of his niece, he mistakenly believes her and her husband have been murdered by the outlaws.
As Robert, William, and Pedro continue their harrowing trek across the desert, the toll becomes evident when William succumbs to exhaustion due to his gunshot wound. Only two of them remain when Pedro suffers a leg injury, leading to a poignant moment where he requests Robert to leave his pistol behind as a signal against any wild animals. Wishing him well with a heartfelt "Feliz Navidad," Pedro eventually fades from the narrative, leaving Robert alone with the infant.
After a grueling journey, Robert reaches a breaking point but finds solace in scripture, reminding him of a prophecy regarding a donkey and its foal. In a miraculous turn of events, he comes across a stray donkey, which ultimately guides him into New Jerusalem, where a Christmas celebration is underway. Just as he enters the saloon, Buck confronts him, demanding him to raise his hands, yet Robert collapses in a blurred view of redemption.
In a twist of fate, Robert finds himself back in Welcome, imprisoned but held in relative high regard by Buck and the townsfolk for his selfless actions toward the baby. With an impending trial, the judge lays down a harsh sentence of 20 years unless Robert relinquishes custody of the child to Buck and his wife. Staunchly loyal to his promise made to the dying mother, Robert stands firm, accepting the lengthy sentence but ultimately winning the judge's favor. Thus, he is sentenced to just a year and a day, receiving heartfelt farewells from the townspeople as he embarks on his journey to prison, cementing his legacy as a steadfast hero in the face of adversity.
