Ep 18. Opposites Interact!

Ash and his friends continue their journey through the Sinnoh region as they come across a young trainer named Marley. Marley seems to have a strange connection with her Pokemon, which are all of the Ghost type. She explains to Ash and the gang that she's on a mission to save a graveyard in the nearby area that is being haunted by a group of mischievous Ghost Pokemon.

Ash and the gang offer to help Marley in her mission, and they soon learn that the only way to combat the Ghost Pokemon is with Pokemon of the Dark type. This poses a challenge for Ash, who has never caught a Dark type Pokemon before. Nonetheless, Ash is determined to help Marley save the graveyard, and he sets out to catch a Dark type Pokemon.

Meanwhile, Team Rocket has their sights set on capturing a powerful Ghost Pokemon that has been terrorizing the graveyard. They concoct a plan to lure the Ghost Pokemon out by using a fake gravestone, which they hope will attract the Ghost Pokemon to their location. However, their plan backfires, and they end up attracting the attention of a powerful Dark type Pokemon instead.

As Ash continues to search for a Dark type Pokemon, he and his friends come across a young trainer named Keith. Keith has a powerful Dark type Pokemon called Umbreon, which catches Ash's eye. Ash challenges Keith to a battle, and the winner will get to keep Umbreon. Keith accepts the challenge, and the battle between Ash and Keith begins.

The battle is intense, with both Ash and Keith pulling out all the stops to win. In the end, Ash emerges victorious, and he earns the right to keep Umbreon. With his new Pokemon by his side, Ash and the gang set out to save the graveyard with Marley and her Ghost type Pokemon.

When they arrive at the haunted graveyard, they find that Team Rocket has already arrived, and they have captured the powerful Dark type Pokemon. Ash and the gang team up with Marley and her Ghost type Pokemon to take on Team Rocket and rescue the Dark type Pokemon.

The battle is intense, with both sides using all of their strength to come out on top. However, in the end, Ash and the gang emerge victorious, and they manage to free the Dark type Pokemon from Team Rocket's clutches. With the graveyard saved and the Ghost Pokemon finally at peace, Ash and the gang bid farewell to Marley and continue on their journey through the Sinnoh region.