In 1896, Jeff Webster (James Stewart) sees the start of the Klondike gold rush as a golden opportunity to make a fortune in beef. He and his friend Ben Tatum (Walter Brennan) drive a cattle herd from Wyoming to Seattle, by ship to Skagway and through the mountains to Dawson City.
On the way, he annoys town boss and self-appointed Skagway judge Gannon (John McIntire) by interrupting a hanging. Webster ends up being taken into custody and jailed. He meets French-Canadian gamine Renee Vallon (Corinne Calvet) at the jail, when she brings supper to his cell mate. Renee immediately takes a liking to Webster and flirts with him.
Webster doesn't have to wait long for trial, and he's escorted to the saloon to meet with the judge. Renee goes along and Webster calls her "Freckle Face," which irritates her. Judge Gannon asks him who he shot. Webster explains it was two men who took it upon themselves to combine his herd with theirs. The judge agrees that was justified, so he dismisses the case, but he also tells Webster his cows are being confiscated for disturbance of the peace, among other things. Webster wants to take issue with that, but he realizes he's badly outnumbered, and justice usually goes to the strongest at the time.
The owner of the saloon, a woman named Ronda Castle (Ruth Roman), asks the judge why he confiscated Webster's cattle. "Because I wanted them," he says.
Webster and Tatum decide to make for the Klondike, even though they lost their cattle, and begin making preparations. Ronda just happens to be heading up a party bound for Alaska with the cows and she offers Webster a job as her trail boss. Since Webster and Tatum are down to their last $50, and it requires a minimum $100 in food and supplies to receive permission from Judge Gannon to head up the trail, Webster agrees to the job. Plus, he's obviously attracted to Ms. Castle and her to him.
Not long into their trip, Webster, Tatum and Ben Rube (Jay C. Flippen), slip off during the night, and take off with the cattle. Gannon and his men pursue. After crossing the border into Canada, Webster uses a few well-placed warning shots to persuade Gannon's gang to give up the chase, but the judge promises a hot reception when Webster returns to Skagway, as he must, for it's the only way to get back.
Ronda and her men re-join Webster to complete the journey to Dawson City. She still considers Webster to be her employee, obliged to see them all safely through. As they approach 2-Mile Pass, Webster announces that they will take a trail through the valley and not attempt to go over the pass. Ronda tells him that she won't accept him taking an additional six days to go through the valley, but he won't be persuaded, or ordered, to do differently. So, Ronda and her group head for 2 Mile Pass while Webster and his men, with the cattle, head for the valley.
What Webster didn't explain to Ronda was that he was concerned about a possible avalanche in the pass. When Tatum asked Webster why he didn't tell her that, Webster just says, "she wouldn't listen." It's not long before there's a loud rumbling noise and Webster and the others look up towards the pass to see a large avalanche taking place. Renee, who's along for the trip, quickly calls for the men to head up there and see if the others needed help. Webster refuses at first, but Renee and Tatum appeal to his sense of morality and he begrudgingly agrees to go with them.
Three members of Ronda's group were killed and other injured. The survivors rejoin Webster's group and they all continue on to Dawson City. Ronda tricks Webster into reaching for her coffee cup, and she kisses him. Renee witnesses that and gets very upset.
When the group get to Dawson, they find widespread (though relatively peaceful) lawlessness. Webster ignores it as none of his business. There's interest in his cattle and Tatum ends up conducting an impromptu auction, where Ronda outbids the co-owners of the local hash house, Hominy (Connie Gilchrist), Grits (Kathleen Freeman) and Molasses (Connie Van).
The people of Dawson City have visions of using their hoped for mining wealth to create a regular town where they can live and raise families. However, Gannon and his gunmen show up in Dawson City and begin cheating the miners out of their claims. One man who takes issue with that is shot to death. The others in town are advised to leave Dawson City and never come back. Dawson has suddenly become a very dangerous place to be.
Webster chooses to stay out of the fray, figuring it's better to stay alive and be able to take another direction in life, if need be, or at least wait until the odds are more favorable. He secretly plans to sneak out and make his way back south, while Gannon is otherwise occupied. He and Tatum get down to the river, where Webster has stashed a raft. However, Gannon had been tipped off when Tatum bought some extra coffee for a long trip, and he and his men ride up on them, shooting and killing Ben and wounding Webster.
Webster manages to load Tatum's body onto a horse, and then gets on his own horse and rides back to Dawson City. No one makes a move to help until Renee sees them and she goes to Webster's cabin and tends to his wounds. She also makes arrangements for Tatum's burial.
Webster is itching to strap on his gun and go after Gannon as soon as he wakes up to find Renee tending to him, but realizes his right hand is wounded too bad.
Ronda comes to the cabin to check on Webster. Renee wants Webster to make her leave, but he allows her to stay, so Renee leaves, angry. Ronda wants Webster to leave things be, as far as Gannon is concerned. She believes if Webster tries to do anything, he'll be killed, but Webster isn't about to let Gannon get away with having murdered Tatum.
Even though his hand is still not healed, Webster decides to strap on his gun and carry his rifle and go face down Gannon. First, he scares off two of Gannon's men who were in the process of placing a notice on his gold claim, identifying it as now belonging to Gannon.
Webster sends his horse down the street, to walk in front of the saloon, where Gannon and his men waited. They were expecting him, so it was very quiet, and they could hear the sound of the small bell attached to the saddle horn (Tatum had been carrying that bell around, intending to put it somewhere in the ranch house they planned to establish in Utah).
Two of Gannon's gunmen, Madden (Robert J. Wilke) and Newberry (Jack Elam), were standing in the dark in front of the saloon, ready to shoot down Webster as he rode up. After they are surprised to see that it's a rider-less horse, they start looking around. Webster steps out of the shadows across the street and yells at them. They all start shooting. Webster is hit by a fragment in his cheek, but he shoots and kills Madden and Newberry.
Webster then calls Gannon to come out and settle the dispute man-to-man. Gannon confirms that his men know when to come outside, then he slips out the back door and sneaks around the side. Before Gannon can complete his ambush, Ronda rushes out the front door to warn Jeff. Gannon shoots her in the back, killing her. Jeff rushes forward and falls down near Ronda, asking her why she couldn't have just gone away.
Gannon and Webster continue their gunfight, shooting at each other from opposite ends of the porch, until Webster shoots and kills Gannon. Gannon's men in the saloon failed to appear in time to help, or save, Gannon. When they did finally step out onto the porch of the saloon, they found themselves facing the rest of the townspeople who were all pointing guns at them. They decide it's time they left town, and they go. Renee rushes up to Webster, ready to help him with his newest wounds.