While Ash wonders what will hatch from his Egg, Team Rocket are also keen to find out. Meowth thinks it might be a Legendary Pokémon, though his teammates have their doubts. Jessie declares that they will steal the Egg, and her teammates cheer to the idea. Later, storm clouds begin to gather, causing Pikachu to get excited from the electricity. Brock says that there is a Pokémon Center nearby and they should get there as soon as possible. A bolt of lightning strikes nearby and ruins Team Rocket’s next plan. The group rushes into a Pokémon Center. Brock eyes off the resident Nurse Joy, but Misty pulls him away by the ear. Joy gives the group a room, admitting they are her only guests for the night.
Meanwhile, Team Rocket waits for the lights to finally dim before breaking into the Center. They tiptoe through the hallway Wobbuffet emerges from his Poké Ball and almost disturbs the peace with his loud shout, but Jessie and the others beat him to the ground. The trio soon reaches the group's room. Meowth picks the lock with his sharp claw. They wonder how they can easily get the Egg, so they tie Meowth onto a fishing pole. They sneak their way in, and then they fuss over who gets credit for the Egg. Though their squabble wakes up Togepi, who Teleports the Egg outside using its Metronome. The trio is startled when Brock starts talking, except it's only in his sleep. The Rockets turn their attention to the Egg again, but it seems to have vanished. They are distracted again, this time by Wobbuffet who appears with an apple in hand. Jessie decides a snack break is in order. Wobbuffet points them to a basket of fruit in the kitchen down the hall. Rushing to the kitchen, Team Rocket trips over Wobbuffet and they all fall flat on their faces. They shush each other to avoid raising any alarms. Later outside, an infant Kangaskhan approaches the odd Egg case with caution. She taps on the glass out of curiosity, causing the Egg to simply roll out of its case. Her mother comes along. She promptly puts the Egg and her baby into her protective pouch before wandering back into the wilderness.
Overnight Ash dreams about the Egg, only it appears much larger. The Egg suddenly cracks, revealing another Egg inside and it keeps going until there's nothing left. Ash wakes up from the nightmare. He looks over at the room’s desk and notices that the Egg is missing. He searches frantically and his shouting disturbs everyone including Nurse Joy. By morning Officer Jenny arrives on the scene, and the police sirens lead Team Rocket to hide in the Center kitchen momentarily. Ash tells her about his missing Egg and Jenny says that she can solve this one right out, they don't call her the Great Police Detective for nothing. A Chansey comes by to see what's going on and Jenny thinks maybe one of the Chansey may have it. Joy inspects her two Chansey, but neither has the Egg. Jenny tries another idea, she gets out her Growlithe in order to search for clues. The Growlithe sniffs Ash to get his scent. Growlithe rushes ahead and leads everyone outside to the empty Egg case. A sudden rustle alerts to who he thinks might be the culprit, but it turns out to be a wild Exeggcute. Joy remembers that there are Exeggcute nests nearby, and so they decide to inspect them. However, this yields no results.
Misty considers checking the Center again, and Jenny leads everyone back to the crime scene. Officer Jenny investigates the room and discovers no signs of forced entry. With that in mind, it must be an inside job, so she accuses Brock of stealing the Egg. Jenny explains her reasoning; Brock got jealous because Misty had her Togepi and Ash had his unhatched Egg. Ash and Misty believe the story, and they ask for Brock to explain himself. Brock collapses to the group and apologizes before realizing that he wasn't the Egg thief. As Jenny pulls Brock away by the wrists, Misty notices some scratch marks on the doorknob. Jenny concludes that Brock must have scratched the knob to make it look like someone else picked the lock. Jenny continues to march off with Brock, but Joy says that there were also scratch marks on the knob on the outside door. Now it can't be Brock since he was inside the whole time.
Jenny decides to use her Jumpluff for another investigation. The Jumpluff sprinkles some pollen onto the floor, which reveals a lot of shoeprints. Nurse Joy explains that she cleaned the floor thoroughly yesterday afternoon, meaning that only Ash's group, she and Officer Jenny would have left any trace. Jenny inspects everyone's shoes and starts to look around. They notice that some different shoe prints that appear to be the closest to the desk. The significant distance between the desk and these footprints is also suspicious, indicating either the thief had long arms or they had a Pokémon assist them. Ash suggests Vine Whip would help and then Misty points out that Ash has a Bayleef. The circumstantial evidence leads Jenny to declare that Ash must be the culprit. Ash pleads his innocence and Misty reminds Officer Jenny of the different footprints. With that in mind, Jenny has Jumpluff sprinkle the hallway for more clues. Jenny spots some Pokémon footprints with her magnifying glass. She declares that the culprit must be a Suicune, but Brock notices that the prints are too small. Unable to actually identify the footprints, the group decides to instead follow the trail.
They spot four face prints, belonging to the Rocket trio and Jessie's Wobbuffet. Brock also points out that James owns a Victreebel that knows Vine Whip. Jenny declares that she knew it was Team Rocket, and her "suspicions" leads the detective party to the kitchen. Officer Jenny reaches for the doorknob but notices it appears to be locked. Nurse Joy explains that the kitchen door doesn’t have a lock on it. In fact, Team Rocket have pushed themselves up against the door. Everyone decides to knock the door down. As they run at the door it gives way, causing them to fall. The Rocket trio flees outside and Ash's group gives chase. They lose Team Rocket at first, but not before finding their footprints on the road. They are soon stopped by Kangaskhan. Brock tells everyone to look because Ash's Egg is in her pouch. Ash tells the Kangaskhan that the Egg is his. Kangaskhan sniffs the Egg, then smells Ash to confirm his story before happily returning the Egg to Ash. Jenny figures that when Team Rocket was running away with the Egg, the Kangaskhan stopped them and fought them for it. Just as this little scene happens, Team Rocket swipes the Egg for real with an extendable grabber hand from their balloon. Jessie sends out Arbok to try to stall Ash and the others for a while, but the Kangaskhan Dizzy Punches Arbok back at them. Jenny calls out her Growlithe to use Flamethrower on the hand, causing it to drop the Egg. Ash catches the Egg and then orders Pikachu to deliver a Thunderbolt which blows up the balloon and sends Team Rocket blasting off. Afterwards, Officer Jenny gives the Kangaskhan a salute and thanks them for their civil service.
Back at the Center, Officer Jenny admits that the missing Egg case had a lot of unexpected twists, though Misty thinks that Jenny made the investigation more complicated. Brock asks Officer Jenny to solve the case of the lovesick Breeder, though Misty apologizes to the Officer before pulling Brock away by the ear. Nurse Joy wishes Ash all the best with the Egg. Soon after, Ash and his friends continue their journey towards Mahogany Town.