Ash is traveling through the forest on his way to Oreburgh City, where he hopes to win his first Gym Badge in Sinnoh. But first he's helping Starly practice using Aerial Ace, a process that doesn't go entirely smoothly. Our heroes also catch the attention of Rosebay, a woman who monitors the Pokemon that live in the forest. Lots of Pokemon have been disappearing lately and she's not sure why, but it doesn't take long for Ash and his friends to decide they should help her out!
Meanwhile, Team Rocket have set up a trap in the Valley Path, an area which Flying-type Pokemon often pass through. All it takes some netting and soon Team Rocket is happily snagging lots of avian Pokemon for their Boss. When Ash sends Starly out to look for clues, Starly is swept up by Team Rocket's criminal plans as well--but Starly isn't about to sit back and wait to be rescued! Jessie and James leave Meowth to guard their ill-gotten Pokemon, and Starly is ready to stage a jailbreak together with help from a captured Hoothoot.
Hoothoot hypnotizes Meowth into letting the Pokemon go, but when Meowth snaps out of his trance, he calls for backup from Team Rocket's other Pokemon. However, Ash and his friends came across a Pidgeot trapped in Team Rocket's net and realized what's going on, and they show up looking for Starly! Jessie and James return to try and stop our heroes, only to discover that Brock's Bonsly can use Mimic to send their Pokemon' moves right back at them. Then Starly evolves into Staravia and pulls off a terrific Aerial Ace--which is also the term that describes Team Rocket as they go blasting off again. The trapped Pokemon are freed, Rosebay is happy, and now it's onward to Oreburgh City!