Ash and friends are walking through the Valley of Steel on their way to Petalburg Gym when they encounter a Torkoal being attacked by a Skarmory and several Magnemite. May's Skitty and Torchic drive the Steel-type Pokémon away.
The Pokémon of the Valley of Steel turn out to be very territorial, and both Torkoal and the kids have put themselves in danger by trying to cross the valley. Regardless, they decide to press on.
Team Rocket is in pursuit, though at first the trio is attacked by Skarmory and later Steelix. They are sent blasting off and nearly hit Ash and his friends on the way down, falling into a chasm instead. May tumbles off the edge, and Ash and Torkoal work together to save her. They are attacked by a Magneton, which Torkoal sends flying using Flamethrower.
Magneton is found by the Steelix, who then goes looking for Torkoal and the kids. When they meet, it turns out that Torkoal came to the valley looking for a fight with this powerful Pokémon. The two begin to fight, with Ash directing Torkoal. Steelix has the advantage until Torkoal uses Overheat, knocking the giant Steel-type out.
Torkoal joins Ash's roster of Pokémon, and the gang leaves the Valley of Steel.
Eager to reach Mauville City, Brock leads Ash, May, and Max into what he believes is a shortcut. Instead he manages to get them hopelessly lost in a bleak looking wilderness, the Valley of Steel. As they look at the map, Ash suddenly sees something strange in the sky, a Torkoal being attacked by a pair of Magnemite and a Skarmory! Ash rushes towards the fight with Pikachu; together, they are able to drive off the angry Pokémon. Happy to be rescued, the Torkoal thanks Ash and his friends by accidentally covering them with soot. Suddenly it hears a noise, and runs off into the distance leaving a very confused Ash behind. Up in the sky, Jessie, James, and Meowth float by in their Meowth balloon. Meowth notices a Skarmory, and translates its cries as a warning for the trio to leave the area. Before they can turn around, the angry Pokémon blast Team Rocket off by slicing open their balloon with a Wing Attack.
Back on the ground, Ash and his friends are about to cross a rocky valley, which Brock claims will get them back to the main road. Suddenly the two Magnemite from before appear, and begin attacking. The group are forced to hide behind some rocks. Pikachu tries another Thunderbolt, but the two Magnemite are unfazed, and soon Ash and Pikachu also retreat to safety. Taking some of Max's advice, May calls out Torchic, who drives them off using Ember. May praises her Pokémon's efforts, while Brock becomes increasingly suspicious of the wild Pokémon's aggressive behavior.
A sudden explosion alerts the group, and it is revealed to be Torkoal, who once again is being attacked by Skarmory and three Magnemite. Ash leaps to the rescue. May decides to join in, just as she and Torchic are about to join the battle, her Skitty emerges from its Poké Ball. May is initially agitated, but Max and Brock remind her that by combining Skitty's Assist and Torchic's Ember, the double attack could prove more effective. May orders an Assist, which turns into Beautifly's String Shot, which tangles the Magnemite trio in sticky threads. Torchic lauches an Ember which frees the Magnemite, though they quickly fly off. Skarmory replies with a Swift attack, and Pikachu's Thunderbolt attracts the Pokémon's attention away from May. Just as SKitty and Torchic are running in to attack, Torkoal uses its Flamethrower which sends Skarmory flying away. The effort causes Torkoal to collapse from exhaustion.
While tending to Torkoal's injuries, Brock tells everybody that they stumbled into the Valley of Steel, a place filled with wild and very aggressive Steel Pokémon. Torkoal probably got lost and was attacked by the Pokémon, just like they were. Ash suggests Torkoal should team up with them, and explains that he is certain that its power, along with their other Pokémon, will be enough to get them safely out of the valley. Torkoal agrees, but suddenly the sound from before rings out, and Torkoal runs off towards it. Brock speculates that the noise might be coming from another Pokémon, one far stronger than the Skarmory and Magnemite. They head in the direction Torkoal ran. In another part of the valley, Team Rocket runs away from an angry Magneton. Its electric attacks send them blasting off for a second time. They land directly in front of a very large and angry Steelix. Not wanting to be attacked, Team Rocket tries to be nice to it by polishing its body. Thinking they have done a good job, Steelix's tail glows a brilliant white. However, Team Rocket is met with Steelix's Iron Tail attack, which sends them blasting off yet again. They land right next to Ash and his friends, who have reunited with Torkoal on the edge of a big crevice. Bouncing away, Jessie, James, and Meowth fall into the fissure, inadvertently knocking May and Torchic in as well.
Grabbing onto a branch, May is able to keep herself from falling to the bottom of the crevasse. But a wild Magneton soon arrives and tries to knock her off using electric attacks. Torchic, Pikachu, and Torkoal all use their attacks to keep it away, while Brock and Max lower Ash down on a rope to rescue May. After successfully dragging May back up, Torkoal manages to hit the Magneton with a Flamethrower, driving it away for good. Injured, the Magneton flies to Steelix's location and tells it where Ash and the others are. Angry, the Steelix uses Dig and begins heading towards them. Ash and his friends finally reach the edge of the valley, which is marked by a river. Before they can cross, the Steelix suddenly comes out of the ground and begins to attack. Brock realizes that this Steelix is the reason Torkoal entered the valley; it wanted to challenge it to a fight to prove its strength. Just as the other Steel Pokémon are about to join the battle, Steelix wards them off with its stern gaze. With Ash giving out commands, Torkoal and Steelix square off in single combat. Ash soon realizes that Torkoal's Flamethrower is doing little damage to Steelix, despite its weakness to fire attacks. Steelix digs into the earth, and Ash anticipates its attack he remembers his fight against Flannery who had her Torkoal perform Overheat. Despite Brock's warning that Overheat gets weaker after each time it is used, Ash orders Torkoal to perform the attack. The gaps in its shell glow red, as Torkoal and Ash wait anxiously. Steelix suddenly resurfaces, but Torkoal manages to land a direct hit. Steelix swats the attack with an Iron Tail, much to Ash's surprise. However, Steelix collapses from exhaustion. Just as Skarmory and the others are about to swoop in on the match, Steelix rises up again. A few moments pass as Steelix and Torkoal exchange intense stares, but the Steel Pokémon retreat. Ash suggests that Steelix finally recognized Torkoal's strength, and the group prepare to finally leave the valley. After crossing the river Ash asks Torkoal if it'd like to join his team. Torkoal tearfully accepts his offer and agrees to become one of Ash's Pokémon, as the journey continues.