Ash, Misty, and Brock are traveling through the forest heading to Cinnabar Island when they hear Officer Jenny's voice calling after a thief. They see a man with a sack over his shoulder and a gun in hand. Ash orders Pikachu to attack, but he refuses after seeing the gun in the man's hand. Once again, the trio hears Officer Jenny's voice, this time ordering a Growlithe to attack the thief. It knocks him down and sends the gun flying from his grasp, giving Pikachu the opportunity to shock the thief with Thunder Shock. However, the Growlithe then turn on Ash and his friends, encircling them as Officer Jenny and two other policemen rush to the thief's side. Confronting the trio, Officer Jenny reveals that the thief was in fact a police officer helping to train the canine police unit. Realizing their mistake, Officer Jenny calls off the Growlithe squad and order them to line up. They sit proudly in rows, and greet the group with a friendly bark at Jenny's command.
Meanwhile, Team Rocket is watching from a nearby tree, commenting that the boss would love it if they captured police trained Pokémon, and James announces he has come up with the perfect plan to steal the Growlithe.
Later that evening, Ash, Misty, and Brock have a meal at the training facility. Reflecting on the bravery of the Growlithe, Ash expresses interest in training Pikachu alongside them in order to improve his battling abilities. Officer Jenny agrees to let Pikachu participate in the training class they will be running tomorrow. During this conversation, Togepi wanders off after a piece of food that rolled to the edge of the tabletop. Seeing it about to fall, Pikachu rushes to save it, but instead, he becomes overbalanced and falls to the ground.
Ash and his friends' sleep is cut short by Officer Jenny's sudden whistle as she wakes Ash up for their training. Realizing it was still early in the morning, Ash goes back to sleep, but Officer Jenny blows her whistle again, this time waking up Misty and Togepi as well. Later that morning, the training begins with an obstacle course that, as Ash is surprised to learn, is to be completed by both the Trainer and their Pokémon. He confidently leads the initial run, though his confidence dissipates when he sees the first obstacle, a wire net under which the runners must crawl. Jenny and her Growlithe make quick work of it, though despite his small size, Pikachu's tail gets caught in the wire and shocks Ash as he attempts to use his electricity to free himself. Next is a high wall, which Officer Jenny and Growlithe scale easily, though Ash fails to get over and falls backwards on top of Pikachu, resulting in another shock for Ash. After the test, Brock questions the wisdom of the training program, believing that Pikachu is already very powerful. When Ash asks if Pikachu wants to be as tough as Growlithe, he bows his head, exhausted from their training. This discussion is interrupted as a van painted to resemble a Growlithe breaks through the wall of the compound.
Team Rocket emerges from the van and says their motto. The van is quickly surrounded by Growlithe as Team Rocket reveals their plan to use the Growlithe to commit crimes. The trio then dons gas masks and begins to spray gas from a bottle marked with a picture of Gloom, causing the Growlithe's sense of smell to be disabled. Selecting a second canister, this time marked with Psyduck, they once again spray the gas around the compound. Everyone who inhales the gas finds that their voice has become high and squeaky. As Officer Jenny tries to order the Growlithe to arrest Team Rocket, she finds that they no longer recognize her voice in its altered state and will not respond.
Quickly changing costumes, Team Rocket put on police uniforms and use megaphone voice changers to impersonate Officer Jenny's voice. The Growlithe, unable to smell, immediately trust Team Rocket and follow their orders to arrest Officer Jenny, tying her up with rope. The trio then begins ordering the Growlithe into the van, as Ash and his friends attempt to stop them. Jessie, still using Officer Jenny's voice, orders the Growlithe to surround Ash and his friends. Their attempts to fight back are foiled by the fact that they left their Poké Balls back in their room. However, Pikachu scares the Growlithe back with an Electric attack.
Jessie quickly changes her costume to resemble Ash, switches her megaphone to mimic Ash's voice, and orders Pikachu into the van with the Growlithe. Pikachu's ears prick up at the sound of Ash's voice, but after a moment of confusion, he stands by Ash's side because of their strong bond. Realizing that they cannot capture Pikachu using fake voices, Team Rocket, using Officer Jenny's voice once more, orders the Growlithe to attack. However, Pikachu leaps into the air and uses Thunder Shock several times to defeat the Growlithe, though the effort leaves him dizzy and unable to defeat the remaining Growlithe.
Suddenly, Jigglypuff enters and abruptly leaves after singing a few notes, insufficient to put anyone to sleep. During this distraction, Officer Jenny frees herself from the ropes and attempts to regain control of the Growlithe. Jessie orders them to attack Officer Jenny, and a Growlithe bites her hand, but then, it remembers Officer Jenny and the memories it had with her. Finally recognizing the deception, the Growlithe turn on Team Rocket, who desperately begin changing their voices. However, they only get each other's voices and Meowth's. Meowth, seeing that their plan was foiled, drives the van out of the yard, with Jessie and James following behind.
As they say farewell to Officer Jenny, Ash realizes that Pikachu doesn't have to train with the Growlithe to be the perfect Pokémon. Brock uses Team Rocket's abandoned megaphone to impersonate Officer Jenny's voice and compliment himself, though this only embarrasses Ash and Misty and amuses Jenny herself. As they leave, Brock, feeling Team Rocket's megaphone is useless, abandons it, only for Jigglypuff to find it.