During the tumultuous years after the Civil War, the notorious James-Younger gang becomes a major threat, targeting banks and trains across the Midwestern United States. Led by the infamous Jesse James, along with Cole Younger and their brothers, this band of robbers wreaks havoc as they search for their next heist.
Things take a deadly turn when Ed Miller, a member of the gang, grows impatient during a bank robbery, leading him to open fire and unintentionally kill a clerk. This disastrous incident results in a shootout, leaving Jesse wounded and ultimately dismissing Ed from the gang, though Ed's brother Clell remains loyal.
On the hunt for the outlaws is Mr. Rixley, a determined detective from the Pinkerton’s agency. Rixley relentlessly trails the gang but is responsible for the unfortunate deaths of a Younger cousin and the youngest James brother, not to mention the losses of several of his own men. Eventually, his blunders force the Pinkertons to retreat. Meanwhile, Jim Younger, who is smitten with a young woman named Beth, faces heartbreak when he discovers her engagement to Ed. At the funeral of Frank and Jesse's younger brother, Jim persuades her to break things off with Ed, leading to her eventual marriage to him instead.
With plans brewing, Clell Miller proposes that the gang ride north in September 1876 to rob a bank owned by "squareheads" in Northfield, Minnesota. However, as word spreads about their activities, the town is put on high alert by the Pinkertons.
The heist goes awry, with the bank's vault locked on a timer, making it impossible to access. In the chaos, a cashier and an innocent bystander are shot dead. As the gang tries to flee, they are met with gunfire from the residents. The confrontation results in the deaths of two gang members, while Clell suffers fatal injuries. Frank is hit in the arm, and the Youngers endure severe wounds.
In their desperate escape, the surviving outlaws set up a temporary camp in the woods. Facing increasing pressure, Jesse decides to continue fleeing, leaving the injured behind as the posse closes in. Reluctantly pushed by Cole, Frank joins Jesse in their flight. During their escape, Jesse reveals his intention to form a new gang upon returning to Missouri, though Frank's apprehension is palpable. They make their way back home while the Youngers are captured by law enforcement.
Rixley interrogates the Youngers in prison, but they staunchly refuse to reveal Jesse's whereabouts. In a twist of fate, Bob and Charley Ford, who have been invited to join Jesse's new gang, see an opportunity for a payday. Rixley entices them with a bounty of $15,000 to assassinate Jesse. Over dinner at Jesse's home, when Jesse adjusts a hanging picture, Bob seizes the moment and shoots him. In his grief and anger, Frank James surrenders to the authorities, negotiating to take Jesse's body home for burial, a request to which Rixley reluctantly agrees.
