A boy discovers a talking, intelligent Pikachuwho wants to work as a detective in a world where people collect Pokémon to use in combat. Ace detective Harry Goodman abruptly vanishes, sparking his son Tim, age 21, to investigate what happened at the start of the narrative. Detective Pikachu, Harry's old Pokémon partner and an adorable super-sleuth that even he finds puzzling, is helping with the investigation.
Tim and Pikachu team up on an exciting quest to solve the complex puzzle after realizing they are ideally suited to speak with one another. Together, they follow clues through the neon-lit streets of Ryme City, a vast, contemporary city where people and Pokémon coexist in a highly realistic live-action setting.
Along the way, they come across a variety of Pokémon characters and learn about a shocking conspiracy that could end this harmonious coexistence and endanger the entire Pokémon universe.