Try For the Family Stone!
While heading toward Sunyshore City and Ash's next Gym Battle, our heroes get lost in a dark forest. They come across a mischievous Murkrow that creates what turn out to be fearful illusions. That Murkrow happens to be in the care of a Trainer named Mitchell, who has a sister named Rhyanna. Mitchell and Rhyanna haven't been speaking to each other since Mitchell took off into the mountains to train with his Murkrow—with the goal of finally beating his sis in battle. Now Rhyanna wants to find a Dusk Stone so she can evolve her Misdreavus into a Mismagius. She hopes the evolved Pokémon will help her brother become happy again. However, the angry Mitchell thinks Rhyanna's purpose is to keep winning battles against him!
That brings us to Team Rocket. Of course, their eyes are on getting themselves a Mismagius and a Dusk Stone, too—and what better way than to steal Rhyanna's Pokémon? With Brock's help, Rhyanna has found a Dusk Stone, which goes to the top of Team Rocket's must-steal list, along with Rhyanna's Misdreavus. But, even with Team Rocket's latest invention, the "Porta-Pidgey Mark Two" robot, the would-be thieves aren't able to hold onto Rhyanna's Misdreavus or the Dusk Stone.
Finally, Rhyanna and Mitchell discuss their issues and make up, happily deciding that the winner of the best of 10 battles between them gets to keep the prized Dusk Stone. And, happy in the knowledge that they helped to reunite the quarreling siblings, our heroes resume their journey toward Sunyshore City.