In Pamplona, Spain, three New Yorkers participate in the annual “running of the bulls.” On the plane ride home, Mitch Robbins tells his friend, Ed Furillo, that their adventures are better suited for younger men. The passionate Ed protests, until Mitch points to their other friend, Phil Berquist, already asleep a few seats back. One year later, on his thirty-ninth birthday, Mitch goes to his son’s school to speak at career day. He begins describing his work in radio advertising, but abruptly changes topic, warning the children to prepare for the inevitability of aging. That night at Mitch’s birthday party, Ed and Phil give their friend a two-week “adventure trip” driving cattle from New Mexico to Colorado. However, Mitch says he cannot go. Just then, a young woman interrupts the celebration and shocks everyone by informing Phil that she is pregnant. When Phil’s domineering wife, Arlene, confronts her husband, Phil argues that he has had enough of their loveless marriage. After the guests have gone, Mitch and his wife, Barbara, discuss the stability of their relationship. Sensing that her husband has lost his passion for life, Barbara encourages him to go on the cattle drive with Ed and Phil. A few weeks later, the three men arrive at Stone Ranch in New Mexico. There, they meet the other guests, including African-American dentist, Ben Jessup, and his son, Steve, as well as ice cream magnates Barry and Ira Shalowitz. Bonnie Rayburn, the lone woman, admits to feeling out of place, but the men urge her to stay. Ranch owner Clay Stone invites the “city slickers” to practice their skills in the corral. Mitch is the only person who cannot lasso an object, much to Ed’s amusement. When the three New Yorkers notice ranch hands Jeff and T. R. harassing Bonnie, they attempt to create a diversion, to no avail. Just then, an old weather-beaten cowboy rides up and admonishes Jeff and T. R. to behave like gentlemen. With menacing self-assuredness, he rides away, leaving Mitch awestruck. That night, the guests learn that the cowboy, whose name is “Curly,” will be their trail boss. Ben Jessup relays a rumor that Curly once killed a man, causing Mitch to fear the journey ahead. In the morning, the guests depart Stone Ranch, driving the cattle toward Colorado. En route, Ed admires Bonnie Rayburn. When Mitch reminds Ed that he is married, Ed declares he enjoys keeping his options open. That night around the campfire, Phil and Mitch suggest that Ed appreciate the benefits of a committed relationship. An argument ensues, until Curly warns them to be quiet. In the morning, Mitch tries to make amends by preparing fresh-ground coffee. However, at the sound of the battery-powered grinder, the cattle stampede. From a nearby bluff, Curly watches as the herd demolishes the campsite. Laughing, he fires a gun, causing the cattle to stop dead in their tracks. After noticing that several animals are missing, Curly orders Mitch to help round up the strays. The task takes all afternoon, and the two men are forced to camp together that night. Mitch watches nervously as Curly hones his knife on a leather strop, surprised when the gruff man reveals a sensitive side. The next day, Curly declares that the secret to a good life is to honor “just one thing.” Mitch is perplexed, however, when the trail boss indicates that the “one thing” is unique to each individual. Just then, they notice a cow writhing on its side. Curly assesses that the animal is about to give birth, and charges Mitch with delivering the calf. Though nervous and disgusted, Mitch pulls out the animal, elated when it begins walking around. He names the calf “Norman.” After determining that the mother will not survive, Curly shoots her. Later, they rejoin the main herd, and Mitch introduces little Norman to his friends. At lunch, he recounts Curly’s advice on finding the meaning of life. When everyone laughs, he invites Curly to join the conversation, but the old timer does not respond, and Mitch realizes that Curly has died. After burying the trail boss, the group sets out under Jeff and T. R.’s direction. En route, Phil, Ed, and Mitch share stories about the best and worst days of their lives. The cattle drive is uneventful until “Cookie,” the drunken cook, drives the chuck wagon over a ravine. Cookie jumps to safety but breaks both legs. Ben and Steve Jessup agree to escort the injured man to a nearby town. That night, Jeff and T. R. drink the remaining liquor and threaten to shoot Norman. Mitch tries to negotiate with the cowboys, but the encounter erupts into a fight. Phil grabs Jeff’s gun and orders the bullies to go sleep off their stupor. Moments later, he breaks down crying, and Ed and Mitch console their friend. Ira and Barry Shalowitz report that Jeff and T. R. have fled. The Shalowitzes want to abandon the herd and return to civilization, but Ed and Phil insist they continue. Mitch does not think they are capable of completing the cattle drive, and in the morning, he departs with Bonnie and the Shalowitzes. However, he later rejoins his friends, admitting he could not let Curly down. Following their intuition, they head toward Colorado. When a thunderstorm breaks, they drive the herd into a forest, navigating the steep terrain in pouring rain. They arrive at a raging river, and Ed, undaunted, leads the animals across. However, Norman is too small to withstand the current and gets swept away. Mitch successfully lassos the calf, but is yanked by the force of the rope into the river. Clutching Norman, he is swept downstream, where Phil and Ed perform a heroic rescue. The next day, they arrive at the ranch and bring in the herd. Rancher Clay Stone welcomes them with appreciation, but when he remarks that the cattle are to be delivered to a meat company, the New Yorkers’ spirits fall. That night, Mitch bids a tearful farewell to Norman. In the morning, Ed, Phil, and Mitch reflect on their experiences. Ed announces his intention to impregnate his young wife, Phil looks forward to “starting over,” and Mitch declares he has found his “one thing.” On arriving at the airport, Mitch kisses Barbara and introduces his astonished family to Norman, who greets them with a “moo.”