Barry trains his Empoleon and Heracross. Impressed by their results, Barry is confident with those two he will win. Empoleon seems to behave strange and suddenly, it attacks Barry and Heracross. Meanwhile, the heroes are about to take a ship to Chocovine Town, where Dawn should compete in the Contest. Ash decided when she wins this Contest, they could just go to Snowpoint City, where the next Gym is located. Ash receives call from Barry and shows him his latest Badge. Barry tells him he can now see him as "a true rival". However, his Empoleon is not feeling good and a bunch of other Pokémon are feeling the same - they attack everyone. Nurse Joy cannot determine what is going on, so Barry decides to solve the matter. The gang offers help because they want to help and go to get to a ship to Iron Island.
Team Rocket is waiting for the twerps. Jessie knows they are going to Chocovine Town, but are surprised to see that they are going to Iron Island. So, they decide to follow them. Ash is impatient, as the boat is slow, but they still see the Iron Island. When they come to the Pokémon Center, Nurse Joy tells them Barry already left. Nurse Joy has figured out that only Steel-type Pokémon are affected for some reason. As they go towards upper stages, they see some Diglett are going away – a Lairon disturbs them because of the pain. Pikachu and Ash go to calm it down. Pikachu uses Thunderbolt, but no effect is made. Pikachu manages to electrocute it, but no effect is done. Ash tries to warn it, but Pikachu tackles him, as the Lairon smashes its head on a rock.
Though ash is unharmed, a Metang comes out, with the same problem. Steelix begins to destroy everything and an Aggron attacks it. Ash tries to stop Aggron, so Aggron uses Flash Cannon, but a man grabs him and gets away. His Lucario uses Close Combat to defeat Aggron. They go away and Lucario uses its Aura and tells his master the area is safe. Ash introduces himself and the man is Riley, who trains with his Steel-type Pokémon on the island. Seeing the Pokémon go angry, he and Lucario went to investigate. They ask Riley how come Lucario is not affected and he explains due to its protective Aura, Lucario shields itself. They ask him if they saw a trainer named Barry, but did not see him.
Barry jumps from a cliff, as he was chased by some Magnemite. Heracross gets him and flies to safety, but the Skarmory attack them. Though they fall, Barry and Heracross land on Team Rocket. Seeing them, Barry's Heracross uses Fury Attack. Lucario uses its Aura to sense anything. Riley has discovered that there is a low frequency that affects Steel-type Pokémon – they are berserk, but do not feel any pain. Riley leads the heroes to the path back to town, but they want to help him. Riley warns them it is too dangerous, but Ash tells him the Pokémon are in danger. Riley asks Lucario and it agrees they should come. Riley accepts, but they must not hesitate to defeat any berserk Pokémon, or they will not save them.
Barry accuses Team Rocket as the ones that did this effect on the Steel-type Pokémon. Team Rocket tells him they did not such thing, so they all follow Barry, who saw a machine. They spot that Team Galactic is actually doing some research, while their Pokémon fight any berserk Pokémon that comes to them. Team Rocket has the element of surprise, but a Steelix pushes them down and they are spotted. The Golbat use Air Slash, but Heracross protects Barry from harm. Barry calls it back and with Team Rocket, sends all their Pokémon. As they go, Lucario senses there are people nearby.
Meowth goes to use Fury Swipes, though the female leader's Pokémon uses Fury Swipes, hitting Meowth. The Golbat use Air Slash and Mud Shot, hitting the Pokémon and pushing Barry and Team Rocket into a cave. They see a statue of Palkia and Dialga and the woman asks them to stay there, taunting them. A researcher asks the leader, Mars, to go with the final stage, which she accepts. Barry calls his Pokémon back for rest. The heroes and Riley spot Team Galactic. Riley senses that the ruins they want to open must be causing this low-frequency sound. Lucario points at the artifact, which Mars puts it in a carving.
A power awakens, as the statues glow and a beam hits a far-away mountain. Lucario gets knocked out and when it stands up, it is possessed by a dark Aura and goes to use Aura Sphere on the heroes...
- Music from Lucario and the Mystery of Mew and Pikachu and Pichu are used.
- Professor Oak's Pokémon lecture: Starmie
- This is one of the few times where Carnivine does not show affection for James after being called out of its Poké Ball.
- This is the only episode featuring Team Galactic in which Saturn does not appear.
- The dub title for this episode may be a reference to the song Stealing My Peace of Mind by Rhian Benson.
- The Finnish title is a reference to a commonly used proverb.
- When Lucario comes out of control due to contact with the beam, its Aura can be seen in a dark color, which is probably a reference to the Shadow Pokémon from Pokémon Colosseum and Pokémon XD: Gale of Darkness, that also do not hesitate in attacking humans and have dark Auras, as well as to Lucario's relationship with Aura.
- The object Mars put in the ruins resembles the image from a map of Sinnoh in the Sinnoh-based Pokémon games turned sideways.
- At the scene where after Lucario gets hit by the beam, the ground's color is the same as Riley's trousers.
- The wild Skarmory were hit by Team Galactic's Golbat's Sludge Bomb despite being immune to Poison-type attacks.