On a tip from Professor Rowan, Ash and Dawn head for Canalave City's Old Chateau to sample its famous delicacy, the Old Gateau. Team Rocket break into the Old Chateau so they can have the cake and eat it too; the building is closed and empty because the power is out—and rumor says the Chateau is haunted! As Team Rocket rummages through the kitchen, Rotom secretly eats all the snacks that Team Rocket tries to swipe. Rotom then takes over the Chateau's appliances and chases Team Rocket throughout the building!

Ash and his friends finally reach the Chateau and check inside. They find a microwave sitting in the middle of the generator room—a microwave that tries to eat Pikachu! The generator kicks in and restores power to the Chateau; while Brock visits the kitchen to make his own Old Gateau, Ash takes Pikachu and Chimchar to train in the garden. But when Rotom turns the lawnmower into a menacing machine, the session is cut short. Then, while Dawn and her Pokémon train inside the Chateau, a fan comes alive and scares them away! Pursued by crazed appliances, Ash and Dawn escape to the first floor to warn Brock.

In the kitchen, Brock proudly presents his friends with the finished Gateau, but Rotom possesses the fridge behind him and attacks! When Pikachu and Piplup fight back, Rotom abandons the appliances and briefly appears in its normal form. By taking over electrical devices, one little Pokémon was able to cause all kinds of trouble! Pikachu and Pachirisu finally stun Rotom after it takes over a washing machine, but it's not done yet. The mischievous Pokémon gives everyone one last zap, then merrily zips away. At least Brock's Old Gateau is safe; while Ash and his friends finally sit down to enjoy the real thing, Team Rocket raids the Chateau's confection display case—and ends up nibbling on nothing more than wax food models!