Steeling Peace of Mind! - S12.E6

On Iron Island, Ash's rival Barry is training with his Empoleon and Heracross when Empoleon suddenly turns on its Trainer. Barry calls Ash and Dawn, who are still in Canalave Town, to tell them what happened—other Pokémon on Iron Island are acting strangely, too! Ash and his friends catch the next ferry to Iron Island, with Team Rocket following them in secret, but Barry has already gone out to explore the island. Whatever is happening, only Steel-type Pokémon are affected, but why?