In Denver, Bret ends up playing poker with Foxy Smith at the local saloon. As the marshal watches, Bret wins to the tune of $2,000 and asks Foxy to pay up. The man checks his wallet and claims that it's missing, but insists that he's good for it. A skeptical Bret takes Foxy's diamond stickpin as collateral and Foxy draws a gun on the gambler, insisting that Bret give it back. A fight breaks out and Bret finally emerges the victor. The marshal, who has been casually watching the brawl, thanks Bret and handcuffs Foxy. He explains that Foxy has been acting suspicious but he had nothing to hold him on, and now he can charge him with disturbing the peace until he can figure out what Foxy had in mind.
In Bubbly Springs, CO, a group of outlaws lead by Cole Younger are using the hotel clerk, Willie Thimble, for target practice. Among the famous outlaws are Billy the Kid and a drunken Sam Bass. Bass manages to shoot a candle off of Willie's head and the outlaws go into the saloon to celebrate. Bret arrives in town and comes to see Willie, an old friend and a jewel fence. Willie tries to warn Bret off, insisting that no one is there and there's nothing to see. Cole comes in and sees Bret with the stickpin, and tells him that he'll round up the boys. Bret assumes that Cole is talking about a poker game and says that all he has is the stickpin, and Cole tells him that'll be enough.
An attractive woman, the famous outlaw Belle Star, comes down the stairs and Cole tells her that Bret has finally arrived. She introduces herself and Cole tells her to get the others. Belle, fawning over Bret, says that a few minutes won't matter and Bret plays along with whoever they think he is. Belle finally leaves to get the boys while Cole takes Bret into the saloon and warns him that Belle belongs to him.
Belle comes in with the other outlaws and Cole insists that he's in charge. He tells Bret to give them his plan and Bret has no idea what they want or who they think he is. The outlaws assume that Bret is playing it cagey and wants to know who he's dealing with, and each of them present wanted posters. Sam realizes that besides Cole, Belle, and Bass, the James brothers, Frank Dalton, and Billy the Kid are all there... and their rewards add up to $73,000 Realizing he can collect the money, Bret continues to play along as Willie comes in. Realizing he needs info, Bret accuses Willie of spying on them and drags him out to the lobby. Willie tells him that they think Bret is Foxy Smith, the brains of their operation. The only thing they know about Foxy is that he wears a diamond stickpin. Cole comes out and demands to know what's going on, and Bret sends Willie on his way with a threat.
Later, Bret counts up the reward money and tries to leave via the window to notify the authorities. However, Belle comes in and asks him about the plan. He refuses to discuss it with her and Bell asks for a drink. When he passes, Belle sits on Bret's bed and invites him to join her. He points out that she's Cole's woman but Belle says that Bret has nothing to worry about. Bret ushers her out but not before Belle kisses him.
Bret then goes out to the stable and mounts up, but finds Billy waiting for him outside. The gambler assures the young outlaw that he's just walking his horse off. However, Cole arrives and fires a warning shot, and tells Bret that none of them are going anywhere. As Billy takes Bret's horse back, Cole asks the gambler why he took so long to get there. Bret tells the truth--sort of--and claims that he Foxy got into a fight with a gambler. Cole tells Bret that he should keep his good-luck stickpin because he's going to need it for the job, whatever it is. Bret goes back into the hotel and Cole tells Billy that he has the outlaws watching Bret to make sure that he's boxed in.
In the Denver jail, Foxy demands that the marshal releases him. The lawman refuses and Foxy warns him that nobody keeps Foxy Smith boxed in.
The next morning, Willie visits Bret in his room and warns him that Cole doesn't trust the gambler. When Bret wonders what to do, Willie suggests that he come up with a plan so wild that even the hardened outlaws will balk. Cole brings Bret down to the saloon and the meeting begins. Bret tries to stall while he comes up with an idea, and a hung-over Bass mentions a mint. Seizing on the suggestion, Bret accuses someone of leaking his plans, saying they were locked up in his rooms. Belle eagerly volunteers that she was in Bret's room to make Cole jealous and the gambler tries to hush her up. Bret shrugs it off and tells them his big spur-of-the-moment plan: they're going to rob the Denver Mint.
Bret warns the gang that they could take anywhere from 50 to 75% casualties but the outlaws see the chance for a big score and demand that he explains. Improvising, Bret says that they'll replace the ten guards, load the gold, and then get away with the loot. The gang is eager to start but Bret tells them that they have to wait. Cole figures Bret is up to something and the gambler claims that gold is coming in from across the state for one big shipment out in three days' time. When the outlaws bicker about whether to wait, Cole says that he'll check out Bret's story with a friend in Denver and make sure Bret's on the level. If he is, they'll wait. If he's not, they'll then check further and see if Bret is really Foxy Smith.
At the Denver marshal's office, Foxy tries to bribe his captor with a year's salary. The marshal declines, saying they haven't had a chance to get fully acquainted.
In Bubbly Springs, Cole gets a wire from his friend. Bret waits nervously until Cole finally says that Bret was right except that the gold will arrive one day earlier than planned. The outlaws apologize to Bret and leave except for Cole, who warns Bret that his friend is still checking on Foxy's background. Cole suggests that Bret demonstrate Foxy's infamous trick shot skill by showing how he can shoot the candle off of Willie's head, laying on his back and aiming with a mirror. They go to the hotel but Bret demurs, twirling his pistol and boasting that he's given up kid's stuff like trick shooting and now only draws his gun when he's going to kill someone. As he walks away, Bret twirls the gun into his holster... the wrong way. Fortunately, only Willie sees it and sighs in relief.
Back at his room, Bret finds Belle waiting for him. This time she's brought her own bottle and admits that she admires Foxy's bloodthirsty reputation. Bret plays along, pretending to be vicious, but the talk soon turns to Belle. He suggests that she might change careers but Belle says that she doesn't know anything else and that she'll ride with the rest of the gang. She kisses Bret and is interested in staying the night, but he says he has to prepare for the heist and she reluctantly leaves.
On the day of the robbery, Bret splits the gang up into smaller groups. Dressed as guards, the outlaws go on ahead and only Cole is left, waiting for Belle. She comes in, dressed as a schoolteacher, and Bret tells Cole to keep her safe. Cole is still skeptical about "Foxy" but Bret assures him that they'll all be rich when they rob the mint. Once they leave, Willie congratulates Bart and they go to the telegraph office. Bret sends a wire to the marshal in Denver, telling him that the unsuspecting outlaws are on their way and that he'll be there shortly to collect the reward.
Bret rides into Denver and heads for the marshal's office. Before he can go in, Belle runs up to him and says that they need to talk. They go to a diner and the waitress, seeing Belle cry, assumes that they're eloping. Bret fends the waitress off and Belle tells him that the marshal and his deputies ambushed them at the mint. When Billy saw them, he panicked and opened fire. With his dying breath, Cole accused Bret of betraying them but Belle doesn't believe it. She warns him that some of the other outlaws escaped and will coming for her and Bret, figuring they were in it together. Eager to get to the marshal and collect his reward without Belle realizing the truth, Bret says that he's going to talk to the marshal at the mint and ferret out who betrayed them. She insists on going and Bret reluctantly agrees as long as she lets him talk to the marshal privately.
When they arrive at the mint, Bret is surprised to discover that Cole is waiting for them. Cole congratulates Belle on playing the part while the outlaws take the gold out. Foxy is waiting in the manager's officer and congratulates Bret on his plan. He admits that it was better than his own plan and that it would have worked perfectly except for two things. Billy ran into Foxy when he arrived in Denver, and Cole paid off the telegraph agent in Bubbly Springs to give him Bret's telegram.
Foxy has Cole stand Bret up and put a small pile of coins on his head. He then lies on his back and aims with a mirror, and manages to make the shot. He tells Bret that the outlaws have plans for him but insists on paying his $2,000 in gambling losses... and then punches Bret. As Cole takes Bret out, Foxy recovers his lucky stickpin back and tells Bret that his luck has run out.
Cole ties Bret up and leaves Billy standing guard until they can load the gold and dispose of the gambler. Bret starts playing on Billy's insecurity, hinting that the rest of the gang will abandon him. Belle comes in and tells a nervous Billy to get out. Once he does, Belle apologizes and Bret says that he understands. He asks for a last smoke and she obliges, and admits that she has lousy luck with men. Belle gives Bret one last kiss as Billy comes back, and she slaps the young outlaw for interrupting.
Bass comes in and tells Billy that they have orders from Cole to stay behind and kill Bret. The older outlaw admits that he doesn't like it and Bret agrees. Foxy comes in and Bret suggests that he might be abandoning Billy and Bass. Billy finally loses his nerve and tells Foxy to kill Bret while they leave with the others. When Cole shows up, Bret knocks over a file cabinet, startling Billy into firing. Cole runs out to the first wagon while Bass and Billy wound Foxy and go to the second wagon. Bret yells at the outlaws in the second wagon that the law is coming and they pull out... right into Cole's wagon.
The two wagons fall over and the outlaws are forced to abandon the gold and ride off. The marshal and his men arrive and the deputies ride off after the gang. The marshal frees Bret and confirms that Foxy is wounded but alive. The gambler takes the credit for breaking up the robbery, and notices Belle slipping out the front. He distracts the marshal long enough for Belle to make her escape, after she blows Bret a parting kiss.
Out on the street, Bret admires the scattered gold bars and the marshal figures that whoever planned the robbery was a genius. Bret concedes the point without going into specific, and the marshal realizes that something is up. He tells Bret to come by his office later to give him the full story and sends a deputy along with him. Bret tries to leave and the marshal points out that he accidentally forgot to put a gold bar back.