On the fifth day of the Pokémon Summer Academy, Professor Rowan has a special assignment for his campers: they'll each team up with a partner and go to the Summit Ruins at night. They're sure to meet Ghost-type Pokémon along the way, but the first team to retrieve the Summit Ruins medal will win! Ash and Angie team up, while Brock's partner is a nervous kid and a macho boy named Kendall wants to be Dawn's partner. Conway's partner is a strange little girl. That night, the teams enter a forest on their way to the ruins, but Conway's partner doesn't seem to be anyone from the Summer Academy...
Ghost-type Pokémon try to spook Angie's Shinx, but Pikachu shocks them into leaving it alone. As for Dawn, her partner runs away as soon as he sees the Pokémon! Conway's partner turns out to be a ghost who hypnotizes him into walking off a cliff, but a Dusknoir appears just in time to save him! Unfortunately, he faints before he has a chance to realize Dusknoir is one of the good guys.
Dusknoir also saves Meowth from the ghost girl, but now everyone thinks Dusknoir is the real menace. According to Professor Rowan, there shouldn't even be a Dusknoir here, unless it emerged from the mysterious cavern discovered in the Summit Ruins.
Ash and Angie reach the Ruins and find the Summit Medal. They've also found the ghost girl—so when they see Dusknoir, they battle it to protect the girl. Big mistake: the girl opens up a swirling portal to the spirit world and tries to suck in Angie and Ash. Dusknoir wakes up in time to save them and blast the ghost girl back into the cavern, which collapses behind her. Everyone realizes that Dusknoir was really trying to protect people from the ghost! Now that she's gone, things return to normal and Professor Rowan awards everyone equal points. That's the end of another day at the Pokémon Summer Academy!