Mitch Robbins (Billy Crystal) and his best friends Phil Berquist (Daniel Stern) and Ed Furillo (Bruno Kirby) are in their mid-30's, and going through a collective early mid-life crisis. Ed is always suggesting adventurous outings or activities that the three can participate in. The latest, running with the bulls in Pampalona, Spain, leaves Mitch with an embarrassing visit to the doctor. Mitch is not altogether happy when Ed eagerly suggests that they go target-parachute jumping shortly thereafter.Some time passes after the trip to Spain, and Mitch wakes to his 39th birthday. Per tradition, his Mother rings him up with a standard speech of her remembrance of the race to the hospital for his birth.Mitch's morning is further complicated when he gets to work and his latest efforts for the radio station he works for are seen as subpar. Per his manager, all decisions must be approved first. Mitch also leaves work to go to Career Day for his son's class. His career is met with below average enthusiasm by the kids, and Mitch soon ends up lamenting the changes that have been made to his job, as well as a small story about getting older.Later that evening, Mitch's wife Barbara (Patricia Wettig) holds a birthday party for Mitch. Phil and Ed show up, along with their wives. Phil's wife Arlene (Karla Tamburrelli) treats him very badly and once again Mitch finds Phil pretending to sleep at the party to avoid talking to her. Ed's girlfriend Kim (Walker Brandt) is a lingerie model in her mid-20's.After cornering Mitch, the two friends tell Mitch of his present: a 2-week cattle drive in the southwest which they'll accompany him on. Mitch is at first excited, but then declines, claiming that he promised his wife they'd visit her parents in Florida.The festivities grind to a halt when a woman named Nancy (Yeardley Smith), one of Phils' coworkers, appears at the party looking for him, saying she missed her period and claiming that Phil is the father of her unborn child. It soon becomes apparent that Phil has been having an affair, and he and his wife Arlene end up in a shouting match that brings the party to a halt.Later on that evening, Barbara, having noticed Mitch's attitude and feelings during the day, tells him that she is concerned that Mitch might be similarly tempted into adultery in a misguided attempt to find some purpose in his life, or perhaps he could drift into contemplating suicide. Barbara suggests that he go with his friends on the cattle drive and see if the experience can help him find a new meaning in his life.Taking her advice, Mitch, Phil, and Ed find themselves on the drive with a number of other people including a father and son, Ben and Steve Jessup, whom are both dentists, Ira and Barry Shalowitz, brothers that run an ice cream business, and a woman, Bonnie Rayburn, who is looking to start a new life after her husband left her.During their time getting ready for the cattle drive, Mitch, Phil and Ed outfit themselves with ranch clothing and practice roping cattle and horse riding. They get into an altercation with two ranch hands named T.R. (Dean Hallo) and Jeff (Kyle Secor), who make unwanted advances toward Bonnie. Mitch steps in to reason with the ranchers. When they threaten Mitch, Phil and Ed step up. A fight nearly breaks out, however, before they can go further, an unnamed, tough cowboy appears, lassoing one of the ranchers to a fence rail and demanding he apologize to Bonnie. When he refuses, the cowboy throws a huge Bowie knife at him, narrowly missing the man's crotch. The rancher immediately apologizes and the cowboy points out that they've been drinking and they need to stop immediately.Later on that evening, the group sits around a campfire and identify the unnamed man as Curly (Jack Palance), the trail boss. Everyone speaks in hushed tones about Curly, but Mitch instantly decides that the man is a lunatic... just as Curly comes up behind him. Curly is tall and intimidating, however Mitch still tries to make conversation with him. Curly isn't moved by Mitch's attempt at friendliness and tells him in a low tone "I crap bigger n' you."A few days later the group head off to drive the cattle across the plains. During the first leg of the trip, Mitch, Ed, and Phil discuss certain questions about life and relationships. Early one morning, Mitch operates a battery-operated coffee grinder he brought, with the noise spooking the cattle and sending them stampeding off. Curly orders everyone to continue the drive with TR and Jeff. With some cattle still missing, Curly decides to take Mitch with him to recover them.Mitch and Curly recover the extra cattle, but end up spending the night out in the wilderness. Mitch is sure that Curly is planning to kill him for what he said about him, especially since Curly makes a show of stropping his knife, which Mitch finds intimidating. Curly tells Mitch to put away the harmonica Mitch'd been playing and Mitch finds the courage to stand up to Curly, telling him he's trying to enjoy his vacation. When Mitch plays the opening bars to "Tumblin' Tumbleweeds", Curly's rough countenance seems to soften a bit and he sings along. During their time alone together, Curly and Mitch begin to discuss life and decisions and Curly seems to gain more respect for Mitch. Curly tells Mitch that the secret of life is 'one thing,' but says that Mitch will have to figure out what it is for himself.Right before they return to the herd, one of the cows goes into labor, and Mitch reluctantly ends up assisting with the birth, pulling the calf from the mother himself. Mitch happily names the little calf Norman. However, Curly suddenly shoots Norman's mother, explaining that she was dying and suffering for it. Mitch seems to understand and decides to watch over Norman himself.After they've rejoined the group on the trail, Mitch explains to them that Curly isn't quite the threatening guy he comes off as and wants the others to chat with him as well. However, when they approach him, they see that he has died while watching over the cattle. Curly is buried on the trail in a solemn ceremony before everyone moves on, with T.R. and Jeff taking Curly's place.Mitch, Phil and Ed share another moment of conversation, talking about the happiest and worst day of their life. Each man has something different: Mitch remembers his Dad taking him to Yankee Stadium for the first time as his happiest. The worst was the day when it seemed that his wife may have had breast cancer -- they later found out she was fine. Phil (surprisingly) remembers his wedding day as his happiest. Every day since, he claims, is a tie for the worst day. Ed recalls the day that his father finally left their family as his happiest, as his father had been cheating on their mother. Ed also claims this as his worst day.Sometime later, the cook known as Cookie (Tracey Walter) gets drunk and ends up destroying the chuck wagon and killing the two horses that pulled it. The incident leaves him with broken legs, and little food left. Later the same evening, T.R. and Jeff get drunk, recklessly begin shooting the empty bottles and threaten to kill Norman the calf. An altercation takes place, with Phil almost snapping, and pointing a pistol at one of them. He regains control of himself and tells everyone that he's actually afraid of guns but knows he should know how to use one in case the store he manages is robbed. T.R. and Jeff to rush off, leaving the others and the herd with no guides. Mitch volunteers to move the herd himself, mentioning that Curly said they would eventually encounter a river before arriving in the valley where the trail ends and the ranch they're heading for is.The Jessups volunteer to take Cookie ahead to the end of the trail; they're the most qualified since they're doctors, despite being dentists. Phil and Ed stay to help Mitch. They manage to get the herd to the river, but Norman gets swept away in the current. Mitch is able to overcome his inability to rope a cow and lassos Norman but falls in the river. Phil and Ed save Mitch and each other, before finally arriving at the other ranch.The ranch owner is excited at what the boys have done, and agree that in reward for what they've done, they'll be refunded their money for the experience. When one of them asks about maybe herding the cows back to the other ranch, the ranch owner claims that the cows will actually be taken to market. Mitch, Phil and Ed are saddened by the news, with Mitch feeling that they are betraying the cows' trust. Although, Ed dismisses' Mitch's guilt noting that the cows have no comprehension of them and simply obeyed their commands on the drive, Mitch finds when he visits the herd, Norman walks up to him as the one whom he owes his life and Mitch finds himself making a decision.During their last day, the three friends decide what to do about their lives. Phil decides that he will graciously start his life over, in the face of his impending divorce. Ed decides to fulfill his girlfriend's request to have children. Mitch meanwhile, has deciphered Curly's 'one thing' saying, which he feels is something different to everyone, what's most important.Mitch returns home to his family, and is eager and happy to see them. He shocks his wife by showing that he has brought Norman the calf along with him to save him from slaughter. After the family and Norman (whom Mitch reassures his wife will be placed in a petting zoo shortly) are loaded into the family van, they head home.