In the Forest of Okoya, Koko is a feral child who has been raised as a Pokémon by the Mythical Pokémon Zarude. Koko has grown up never doubting that he is a Pokémon even though he can't really use any sort of moves. Ash Ketchum and Pikachu meet Koko and help him protect the Great Tree from the crooked scientist Dr. Zed.

In San Francisco, Jill Valentine is dealing with a zombie outbreak and a new T-Virus, Leon Kennedy is on the trail of a kidnapped DARPA scientist, and Claire Redfield is investigating a monstrous fish that is killing whales in the bay. Joined by Chris Redfield and Rebecca Chambers, they discover the trail of clues from their separate cases all converge on the same location, Alcatraz Island, where a new evil has taken residence and awaits their arrival.