The movie opens with Mitch Robbins (Billy Crystal), back in Colorado, riding a white stallion to visit deceased trail boss Curly's grave. Mitch thanks Curly for the time they spent together and says that he truly changed his life. Just then, Curly (Jack Palance) rises from his grave and drags down Mitch who screams until he awakens in his New Rochelle home, realizing it was just a nightmare. He soon forgets the bad dream when the phone rings and it is Mitch's yearly call from his mother who retells the story of his birth and wishes him a happy 40th birthday. Unlike his 39th birthday, Mitch's outlook on life has changed drastically in the last year as he welcomes his 40th one with open arms. His wife, Barbara (Patricia Wettig), informs Mitch that after his birthday dinner, she made arrangements for them to have the whole house for themselves and advises her husband to save up all the energy he can because he will need it.Ever since he returned from his cattle drive adventures the previous year, Mitch has made quite a few changes to his life which now makes him much happier. He moved his family out of the city, kept Norman the calf who is now all grown up and has made a lot of progress at work which lead him to get promoted to station manager.Going into work, he meets his best friend Phil Berquist (Daniel Stern), who Mitch has recently employed at the station. Unlike Mitch, Phil's life has not gotten better over the last year. He got washed up in his ugly divorce with his ex-wife Arlene and now suffers from loneliness to the point where he considers trying to get back with Arlene, which Mitch equates to a criminal willingly checking himself back into Alcatraz prison. To help him out of his funk, Mitch invites Phil over for his birthday dinner with his family.On the train ride back home, Mitch swears he sees Curly on the train but it turns out to be a stranger that just looks like him. The nightmare and the vision lead Mitch to wonder aloud if Curly was truly dead when they buried him but Phil believes that Mitch is just seeing things, since they checked Curly and confirmed he was dead before burying him.When they arrive home, Mitch is shocked to find his younger brother Glen (Jon Lovitz) has arrived unexpectedly. Mitch has a strained relationship with his brother because he is mostly immature, irresponsible, keeps borrowing money from everyone without ever returning it, moves from one relative to another without an invitation until he gets thrown out, and has an irritating fixation on the Godfather trilogy. Seeing how Barbara is already irritated by Glen's presence and wanting to be alone with his wife, Mitch arranges for Glen to leave with Phil after dinner.Finally alone with Barbara, Mitch, looking to role play for his wife puts on Curly's hat and feels something poking him. He then finds a piece of paper, with a missing corner, hidden inside the hat that looks like a treasure map supposed to lead to one million dollars worth of gold bullion and dated from 1908. Interrupted by his wife, Mitch hides the map but then sees Curly staring at him from outside his window and screams.The next day, back at work, Mitch tells Phil that he saw Curly again but when he went outside he had disappeared. Phil questions Mitch as to why Curly would travel all the way to New Rochelle and Mitch reveals the map he found in Curly's hat. Interrupted by Glen, Phil takes the map and heads to the library to do some research. Meanwhile, Glen inquires as to why Phil has a job at the station but not him since he asked Mitch for a job a few months ago. Mitch reveals he doesn't trust Glen since he pulled some strings in the past to get him a job and Glen never bothered to show up. Glen is deeply hurt and leaves but Mitch convinces him to come with him and Phil to a Las Vegas business convention they are attending over the upcoming weekend where Glen might make business connections of his own.Mitch then joins Phil at the library where they analyze the map and surmise that it belonged to Lincoln Washburn who robbed a Western Pacific train carrying gold back in 1908. Quick calculations tell them that one million dollars worth of gold back in 1908 would now be worth about 20 million dollars (in 1994). They also find that the trail starts not far away from Las Vegas where they happen to be going in just a few days. Mitch is reluctant to pursue the treasure or even believe it exists until they find a picture of Lincoln Washburn and realize he was obviously Curly's father. Having already invited Glen for the weekend, Mitch decides to let him in on the treasure and offers him to join them. He also lies to his wife about missing out the convention and potentially jeopardizing his career.The three of them rent horses and supplies from store owners to whom Mitch tries to lie about their motives but quickly finds out Phil has already told them everything. Following the awkward encounter, the three of them head out to find the treasure.After being lost for a moment, they find the very first indicator that the map is real when they find a rock formation that looks like a hand pointing the way just like the map says. However, their excitement is short lived when Glen accidentally sets fire to the map and Mitch almost falls off a cliff to retrieve it. Fortunately, Glen only burned a small hole and they are able to continue their journey. Mitch decides to draw a copy of the map in case of another accident and give it to Phil which causes an argument because Glen whines about his brother not trusting him again. Mitch then gives the copy to Glen.The next day, Phil stops for a bathroom break. As he's squatting, he feels a painful sting on his butt. When he turns around, he finds a rattlesnake and believes he was just bitten. Thinking he is about to die, having heard a horror story from the store owners earlier, he pleads with his friends to suck out the poison. After a short argument, Mitch prepares himself mentally and is about to do it when he finds a cactus spine embedded in Phil's butt cheek. Phil gets emotional when he realizes what his best friend was willing to do to save him. The journey resumes and soon they find more road indicators featured on the map letting them know they're on the right path.As they're having a lunch break, they are interrupted by the store owners who show up with guns to steal the map. They surrender the copy of the map and the store owner ties them up. Just as they're poised to kill them however, a familiar face appears and fights them off. Mitch assumes his thoughts that Curly was not dead are correct, but their savior is actually Duke (Jack Palance), Curly's identical twin brother. Duke reveals he was indeed on the train and outside Mitch's house that night. He explains that long ago, their father had plans to find the gold with his sons once he was no longer being monitored, but he died before it could happen and without ever telling his sons about the map. On her death bed, a year ago, their mother gave Curly the map, and he contacted Duke to come find him so that they could seek the gold together, but he then died shortly after. Duke learned from Curly's friend Cookie that Mitch had taken Curly's belongings, and so sought him out to get the map and claim his family's treasure. Duke then asks for the map but Glen tells him the store owners took it from them. Fortunately, Mitch reveals they took a copy of the map that will only lead them to the closest highway, which causes another row with Glen, and gives the real map to Duke. Duke takes the map and sends them away, intending to find the treasure on his own much to their disappointment. In a moment of courage, Mitch chastises Duke for his attitude, reasoning that Curly would not approve. Mitch explains that Curly was a friend and how Curly explained his philosophy about life ('One thing, just one thing'). Surprised that Curly told Mitch about his "one thing" philosophy, Duke realizes Mitch was someone Curly must've liked. Out of respect for Curly's memory, Duke agrees to let Mitch, Phil and Glen join him, provided that Duke gets half and the three of them have to split the other half amongst themselves.On the road, Duke reveals that, while Curly was in love with the land and cattle driving, he was in love with the sea and spent most of his life in the Navy and then working on all kinds of ships and boats, having traveled the world several times . As they're riding, Mitch sees a wild white stallion just like the one he rode in his dream. Feeling he should ride with it, Mitch chases it for a while until he's able to touch it, feeling elated from the experience. Unfortunately, the scared stallion soon returns with a whole mob of wild horses and Mitch and his friends get caught up in a stampede which destroys most of their supplies and equipment. Mitch is able to save Glen's life which draws them closer. However, Duke reveals that the stampede caused him to loose the map. It also destroyed Mitch's cell phone which guarantees Barbara is about to find out Mitch did not go to the business convention. Things seem grim until Glen tells the others that due to his photographic memory, he's able to recall the last part of the map. With no other choice but trusting Glen or heading back to Las Vegas, Mitch decides to give Glen a chance and the group resume their journey.That night, they get caught up in a cold storm. Out of matches and supplies, the men are desperate to keep warm and not freeze to death when Phil suggests they cuddle together to share their body warmth. Mitch invites Duke to join them but he adamantly refuses. Duke then asks Mitch if Curly ever spoke about him to which Mitch has to admit he never did. Duke then asks if Curly died happy which Mitch confirms he died doing what he loved best. Duke then reveals he had not seen Curly for a very long time but is still sad to have lost his brother. He then reveals that he lost his boat two years ago and have been working at a seafood restaurant impersonating a happy pirate which he absolutely hates. The reason he is so passionate about finding the gold is because it would allow him to retire at sea, his one last dream.The next morning, having survived the cold, Duke pulls a prank on Mitch by pretending to have died just like Curly. He then shows Mitch that Glen was right about the last part of the map as he can see the "buffalo's back" and the "frozen people" Glen was recalling from the map. They find a cave and, after a little fright and more shenanigans, they find a chest filled with gold bullion. As they're celebrating their discovery, they find themselves set upon by bandits. A fight ensues and Glen gets shot while trying to save Mitch. However, Duke soon realizes the bullets were blanks with paint pellets. Just then, another familiar face shows up: Clay Stone (Noble Willingham), who was in charge of the cattle drive ranch where Curly worked and where Mitch and his friends went the year before.Clay reveals that the gold is just lead covered in gold paint and the bandits are actually his sons acting their part. He explains that he invested in one of Curly's idea to take tourists out on a western treasure hunt adventure. The tourists were given printed copies of a similar map Curly had in his hat. Stone also reveals that Curly used to come to the same cave often but never found anything, hence why he allowed Stone to copy the map. Duke inquires as to why Curly would tell him they would get rich to which Clay Stone explains that the endeavor promised to be quite lucrative and Curly wanted to give Duke a piece of the action. The four men are quite brokenhearted that their whole journey turned out to be fake and they were dumb enough to believe it, especially Duke.With nothing left to find, Duke thanks Mitch for being Curly's last friend and parts ways with the three men, having decided to keep looking for the gold. Before he leaves, he reveals he never understood Curly's "one thing" philosophy, which Mitch explains. Mitch, Phil and Glen then reflect on their adventure and realize they are quite proud of what they've accomplished even though the treasure was not real. They did it on their own, without luxuries, and they all found true values in themselves as they all tried to save each other's life at one point or another. Mitch tells Glen he is proud of him for the first time in his life which draws the brothers even closer.Mitch returns to Las Vegas, preparing for a night of trying to reconcile with his wife after having explained everything to her. However, he is surprised when Duke shows up in his hotel room. Duke reveals he finally found his "one thing" in life and it is honesty. He reveals he was planning to cheat Mitch, Phil and Glen out of the gold all along but found himself unable to. He then reveals a secret he had purportedly kept from the other three: the map that Curly had, which was also used as a tourist attraction, had a corner missing. Duke then provides the missing corner, revealing that his mom had given the map to Curly but had taken out the last part and sent it to Duke to make sure the brothers would have to reunite if they ever wanted to seek the treasure. The missing piece reveals that, in 1909, Lincoln Washburn had relocated the treasure further away into the mountains where Curly's map stopped. Mitch thinks that Duke is just messing with him, until Duke produces a solid gold bar...the real thing. He then adds: "It's got friends!" Mitch and Duke starts singing "come and get me" as the two celebrate having found the real treasure.