As the movie opens, we see a guy climbing along the underside of an outcropping from a tall mountain peak. He turns out to be Gabe Walker, a ranger with Rocky Mountain Rescue. (Yes, that makes him "Ranger Walker," and he is addressed as such several times during the course of the movie.) He is in communication with his co-worker and girlfriend, Jessie, who is on a chopper piloted by an older co-worker, Frank. The three are mounting a rescue of yet another co-worker, Hal Tucker, and his girlfriend Sarah, who is on her first climb. Hal and Sarah made it to the top of the mountain, but Hal has aggravated an old knee injury and can't make it back down.
Gabe makes it to the top of the peak where Hal and Sarah are. The chopper drops Gabe a cable, which he secures, while the chopper lands on a nearby peak. All is set for the three to shuttle across the cable to where the chopper is. There is a lot of light-hearted banter as this is a routine operation that they all (except Sarah) do all the time. Hal goes first, and as he is crossing, Gabe asks Sarah how Hal persuaded her to accompany him on this escapade. She replies laconically, "He told me it's better than sex."
Hal makes it across and now it's Sarah's turn. She is a little frightened at the thought of hanging from a cable 4,000 feet above the ground, but the fact that Hal crossed without incident is reassuring. Halfway across her equipment fails and suddenly she is hanging by a strap and unable to reach and grab onto the cable. Gabe quickly crosses to her and grabs her arm just as the strap breaks free. But they are unable to keep their grip on each other, and Sarah falls 4,000 feet to her death. This is by far the most dramatic and gripping scene in the movie and some viewers will be haunted by it for weeks afterwards. But really, except for providing some background for the interpersonal dynamics among the remaining characters, it has nothing to do with the plot of the rest of the movie.
Fast forward eight months, and we pick up two different plot lines that will converge later. At the U.S. Treasury office in Denver, Treasury Agent Travers is preparing to leave on a flight with several large containers of printed currency totaling $100,000,000. His boss introduces FBI Agent Matheson, who is being transferred and is bumming a ride on the flight. Gabe, meanwhile, drives up to Jessie's (and formerly his) house. He had left after Sarah's funeral because he felt he had to get away, and has been working in Denver. He wants Jessie to come to Denver with him, but she won't. She leaves for work, leaving Gabe to get his stuff from the house and load it into his vehicle.
On the plane, Matheson looks out his window and sees another plane flying next to them. He quickly and correctly sizes up the situation, informs the other two Treasury agents that Travers intends to hijack the plane, and pulls his gun on Travers. The other two agents dutifully pull their guns on Matheson, as does Travers. Travers shoots the other two agents, then shoots Matheson. In the cockpit, the co-pilot comments about the gunfire, and the pilot shoots him. The two planes move into position and run a cable between them. Travers transfers over, then the pilot sends the containers.
But Matheson isn't dead. He manages to shoot the pilot, shoot the cable in enough places that it detaches from both planes and the containers fall to the ground, and shoot the other plane enough times that it crashes in the mountains, before his own plane explodes from explosives previously set by Travers. Kristel, the pilot of the other plane, radios for help, reaches Jessie, Hal, and Frank, tells them they are hikers who got lost in a snowstorm, and asks them to send a chopper. But they can't send a chopper because of the storm, so Hal sets off to climb to their location.
Jessie goes back to the house and tries to persuade Gabe to help Hal, but Gabe makes some excuses about not having climbed in so long and drives away. Meanwhile in Denver, Treasury agents are discussing the fate of their plane, when some FBI agents arrive and inform them that Matheson wasn't just along for the ride, he was investigating. Seems that one Eric Qualen, a former military intelligence guy, has been plotting to hijack one of these Treasury shipments. Although the bills are in denominations that aren't distributed and therefore wouldn't have any value to the ordinary thief, Qualen has the international connections to dispose of these bills profitably. FBI shows Treasury, and us, Qualen's picture, and sure enough, it's the head bad guy from the second plane.
We now find Gabe, who apparently has reconsidered since talking with Jessie, climbing up the side of a cliff. At a level point halfway up he meets up with Hal (who still blames Gabe for Sarah's death and isn't particularly thrilled to see him), and they climb to the top, where they are captured by Qualen's party. The three money containers have tracking devices, and Qualen intends for Hal and Gabe to guide them to each of the three locations. They reach a point several hundred feet below the first one and send Gabe up to get it. Qualen insists that Gabe leave his coat behind, a demand that serves no apparent purpose except to uncover Stallone's muscular biceps for a portion of the movie. When Hal warns Gabe the bad guys plan to kill him when he comes down, the bad guys start shooting at Gabe. This only triggers a snowslide that sweeps one of the bad guys over the cliff and... well, you know. The snowslide also sweeps the money container over the edge, where it pops open and sends $33.33 million worth of bills floating through the air and down into the valley below.
Meanwhile Jessie, having grown suspicious over inconsistencies in Hal's radio communication, has Frank drop her off up in the mountains, where she meets up with Gabe. They manage to reach the second container before the bad guys, who arrive to find not the money but a note offering to trade the money for Hal. Qualen realizes it's Gabe and, night having fallen, sends a bad guy out with night vision goggles. This guy finds Gabe and Jessie, but Gabe temporarily blinds him by shooting a flare in his night-vision-sensitive face. The two wrestle and end up sliding down what is literally a slippery slope. At the last second Gabe is able to anchor himself while his adversary goes over the edge and... well, you know. Watching all this from his higher vantage point, Hal comments, "Gravity's a bitch, isn't it?" The bad guys fail to see the humor.
It being night on a snowy mountain, Gabe and Jessie use the money to make a fire, Gabe commenting on how expensive it is to heat the place. Come daybreak, they try to reach the third container before Qualen's group, but their way is blocked by a series of explosions set off by Qualen. One of the bad guys corners them in a cave that was part of their shortcut, but Gabe is able to kill him by impaling him on a stalactite or stalagmite, I can never remember which is which, but this is the kind that comes down from the ceiling and Gabe has to push him up; you get the picture. There is also a scene where a rope breaks and Gabe ends up holding on to the side of a cliff with one hand and Jessie with the other. There is a close-up of their hands holding onto each other that looks very much like Gabe and Sarah's hands at the beginning, but they manage to maintain their grip until Gabe pulls Jessie to safety.
Meanwhile the Qualen group encounters a couple of Bill and Ted wannabes and starts shooting at them, killing one and wounding the other as he parachutes off a ledge. Frank finds the survivor and decides he'd better find out what is going on. He soon discovers the Qualen party and lands the chopper in order to rescue them, only to be shot and killed for his trouble. At this point, Travers wants to forget the money and just get away in the chopper. Qualen demands the tracking device, which Tranvers gives him, but he refuses to tell him the passcode (knowing that if Qualen knew the passcode he'd have no need to keep Travers alive). Travers pulls a gun on Qualen, but Qualen comments that they can't use the chopper without a pilot, shoots and kills his pilot Kristel (who is apparently in love with him; Qualen tells her that the essence of love is sacrifice as he pulls the trigger), and observes that now he is the only one left who can fly the chopper. He orders Travers to take his tracking device and go find the money and bring it back to the chopper. Travers sets off with Hal and the only other remaining bad guy (the one who just shot Frank).
Gabe sends Jessie back for help and sets off to find the last container, getting there before Travers and stuffing the money in his backpack. When Travers realizes he is close and doesn't need a guide anymore, he tells his companion to kill Hal, but Hal manages to kill him first. Travers sees his companion's body sailing down from the ledge and thinks it's Hal, although it doesn't seem to phase him that he never sees either of them again. His tracking device leads him to a rabbit wearing the device from the last container. Travers, a bureaucrat who has watched a seemingly foolproof plan completely unravel, is by now essentially insane. He begins erratically shooting at the rabbit, repeatedly missing it even at close range.
Travers radios that he is going to look for Gabe, alarming Qualen by revealing information about their identities that might be of interest to searchers. Qualen, concerned that someone might have located the origin of the transmission, takes off in the chopper. Travers finds Gabe (or vice versa, it's hard to tell) on a wooden bridge over a mountain stream, and in the struggle that follows, Gabe falls through the ice and into the freezing cold water, which is nonetheless warm enough that he feels the need to take his shirt off and expose his physique once again. Travers spots Gabe under the ice trying to break through to the surface and draws his gun, but Gabe draws his own gun and fires through the ice, killing Travers. Hal shows up and helps Gabe out of the icy water.
Jessie sees the chopper and, thinking that it is Frank, waves for help. Qualen captures her and radios Gabe and Hal that he has her, demands the money, and they agree on a rendezvous point. At the rendezvous, Qualen demands that Gabe throw the money into the chopper or he'll shoot Jessie, but Gabe says that if he does he'll throw the money over the cliff. Qualen relents and drops Jessie off nearby and returns for the money, but Gabe throws it into the chopper blades, and as Qualen struggles to regain control, Gabe attaches the chopper's winch to the top of a metal ladder running down the side of the mountain, while Hal shoots at the chopper until it loses power and falls. It pulls the top part of the ladder off of its attachments and ends up dangling on the side of the cliff. Gabe, who had taken refuge on the ladder to avoid Qualen's gunfire, falls and lands on the chopper, where he and Qualen engage in a fistfight.
As you watch the gray-haired Qualen tangle with the Rocky-Balboa-like Gabe and wonder how it's possible that Qualen isn't having the living crap kicked out of him, you'll need to remind yourself that (a) John Lithgow and Sylvester Stallone are actually less than a year apart in age and (b) Qualen is former military intelligence while Gabe is just a hokey park ranger. But he's a hokey park ranger who can scale the side of a perfectly vertical cliff. As the rest of the ladder gives way, Gabe jumps off and grasps the side of the cliff, while the chopper, with Qualen in it, falls 4,000 feet and explodes on impact.
Hal and Jessie toss Gabe a rope and help him to the top. They are then contacted by Treasury agents in a chopper, who have been monitoring radio communications for the last little while. They tell the trio that they will be back to pick them up shortly. The movie ends with Gabe, Hal, and Jessie sitting on top of a mountain peak, looking very much like Gabe, Hal, and Sarah at the beginning.