Graves is a Wyoming based smokejumper, someone who jumps into forest fires to rescue the unfortunate souls caught in the blaze. During one such blaze, a panicked couple run up to Jesse and Wynt and inform them that their daughter Tina is trapped in their house. Jesse runs into the house, followed by Wynt, and they find the girl hiding inside her dollhouse. They then try to make a run for it, but an explosion knocks over a caravan, which falls on Wynt's leg. Jesse pulls him out and they take cover with the others as a plane called the Big Dipper flies over and deploys Sky Jell-O, dousing the fire.
One year later, Wynt is returning to work at the station after the injury he suffered left him with a limp. Jesse is seen training new smokejumper recruits, including Sherman, who accidentally drops his axe while dangling upside down above Jesse. Jesse decides that he isn't ready for smokejumping yet and assigns him to a ground crew. A gang of criminals have also organized a prison break and get caught in a wildfire. Jesse, who is flying over the forest, spots them walking towards the fire. He jumps down to meet them and explains that they are walking towards a backfire; a fire he lit to draw the oxygen away from the main fire. He then accompanies them to the supply post and goes inside. Shaye orders Karge to go and kill him, revealing his true self to Jennifer. He tells Packer and Loomis to get in a nearby car with Jennifer, where Packer continues trying to charm her, while Shaye goes to get Karge.
In the supply post, Karge attacks Jesse with an axe but Jesse defends himself with his own axe. He proves that he is able to hold his own until Karge knocks a shelf down on top of him. Outside, Shaye bars the door shut and covers the shack in gasoline. Karge tries to exit, but finds himself trapped. As the cabin begins to go up in smoke, Karge demands to know what Shaye is doing. Shaye replies that he's going to take the money for himself and then fires his gun through the door three times; Karge is struck in the face and killed, falling back into Jesse's arms. Shaye leaves with the other two and Jennifer, telling them that Jesse killed Karge but will soon perish in the fire. What they don't know is that Jesse escaped the supply post on a motorcycle.
Meanwhile, Wynt arrives just in time to rescue those trapped in the prison bus and they make it back to the station, where the police are informed of the prison break. The chopper returns without Jesse; the pilot explaining that he jumped. Wynt realizes that the people Jesse went to join were Shaye and his men. Back in the forest, Shaye explains to Loomis and Packer that the police will be searching for them and checkpoints will be set up, so they are going to escape by boat as they won't be checking the rivers. This means that they are headed for the lake. Suddenly, a tree falls in front of the car and they get out to investigate. Jesse bursts through the smoke on the motorcycle and pulls Jennifer to safety. The criminals get back in the car and chase after them until Jesse drives straight over a hill, parachuting to safety in the river below. The villains crash the car and continue on foot.
Jennifer reveals to Jesse a box containing two bird eggs and also explains that she was in the Marine Corps for a while. She lights a signal fire to notify the station that they are alive. Back at the station, Wynt is told that an unidentified body has been pulled from the supply post and he fears for Jesse's life, until Monica tells him about the signal fire. Wynt then decides to go into the fire himself to help Jesse as the main fire and back fire are on a collision course. When they meet, a firestorm will occur and suck up all the oxygen. In the forest, Packer is walking over a ridge while Shaye and Loomis trail behind. They are casually talking until Shaye suddenly shoves Loomis over the edge and he falls to his doom. Shaye tells Packer that he slipped and the two carry on.
Eventually, they catch up to Jennifer, and Packer gets angry that she didn't trust him when he earlier said that he'd let no harm come to her. Jesse suddenly jumps out of the tree above him, managing to snag Packer's leg and leaving him suspended upside down. Shaye tries to shoot Jesse, aggravating Packer as Jesse is holding him up. Jesse lets go of the line but Packer remains dangling above the ground. Jesse vanishes into the smoke, allowing Shaye to capture Jennifer. Packer berates Shaye and orders that he cut him down, but Shaye instead shoots him to death and leaves his body hanging from the tree.
While Jesse follows Shaye and Jennifer to the lake, someone appears behind him. Jesse is relieved to find it's Wynt, and the two lie low and watch Shaye pushing Jennifer into a boat. Jesse tells Wynt that he knows it was him that started the fire; Wynt explains that he only did it for a land developed in order to build a school for firefighters. He knew nothing about the prison break. Jesse tells Wynt that he is not to blame and promises not to tell his friends about the crime. Jesse then heads off to try and sneak up on Shaye, but Wynt pulls out a gun.
Jesse watches as Wynt appears on the dock and reveals himself to Shaye, admitting that he started the fire and was set up by Shaye's lawyer. He then manages to shoot Shaye in the leg, but Shaye returns fire with a shotgun and Wynt takes a fatal wound to the chest. Jesse falls into the water as Shaye turns the shotgun on Jennifer. Before he can kill her, Jesse bursts out of the water and throws his axe into Shaye's chest, knocking him out of the boat.
Jesse swims over to Jennifer, just as the fires meet and the firestorm occurs. He turns the boat over and they both hide underneath, holding it down to keep the oxygen in. Shaye's hand breaks the surface of the water and he fires his gun at the bottom of the boat, blowing a hole in it. Jesse dives back underwater as Shaye grabs Jennifer. Jesse then swims back up and grabs hold of Shaye, shoving his head through the hole and causing his face to burn until there's nothing left. It then begins to rain heavily, drowning the fire.
Jesse and Jennifer swim to shore, where they wait to be rescued. Jennifer reveals that the bird eggs have hatched and Jesse points out how ugly they are, but notes that he can get used to it. Just then, the other smokejumpers arrive to help them, but Sherman once again drops his axe and it barely misses Jesse, who merely sighs.