Evolution by Fire!
On their way to the Icirrus City Gym, Ash, Iris, and Cilan decide to spend the night at the Pokémon Battle Club in Astilbe Town. There they witness a Double Battle between two Trainers: Shamus, with his “Fire Warriors” Heatmor and Emboar, quickly defeats Kylan, with his Mienshao and Watchog.
At dinner, Tepig seems to recognize Shamus and goes bounding up to him. Iris reminds Ash how he and Tepig met after it was abandoned by its Trainer in Accumula Town—and based on Tepig’s reactions, it appears Shamus was that Trainer! Ash and Iris are furious and demand an apology for how he treated Tepig, but Shamus insists he left Tepig behind for its own good because it was too weak to battle.
Don George suggests that Ash and Shamus resolve their differences with a Double Battle. Shamus plans to use his Fire Warriors, and Snivy—who also had problems with its original Trainer—volunteers to be Tepig’s partner for the battle. But Tepig is reluctant to battle against Shamus, remembering how they parted in tears.
As the battle unfolds, Shamus reveals that he was faking his emotional goodbye so Tepig wouldn’t follow him! Tepig is utterly destroyed by this, and despite the type disadvantage, Snivy bravely steps up to take on the Fire Warriors all by itself. Inspired by its friend’s courage, Tepig resolves to prove its strength—and then evolves into Pignite!
The battle really heats up, and Pignite quickly shows that Shamus underestimated it, taking down the Fire Warriors by itself. Defeated, Shamus finally apologizes to Pignite and tries to convince it to rejoin his team—but Pignite sends him on his way with a fiery refusal, and our heroes are off to Icirrus City once more!