A powerful Pokémon sets fire to a lab and then causing a fatal car accident in Ryme City, a place where the creatures and humans live side by side without battles or trainers. In another city, 21-year-old Tim finds out that his estranged father, Harry, a renowned police detective, was killed in the accident, so he travels to Ryme City to collect his father's effects. While staying in his father's apartment, Tim discovers that his father's Pikachu partner -- previously believed dead -- is alive, but without any memories. Tim can understand when the Pikachu speaks, while everyone else still hears the typical "Pika Pika." The duo also discovers that a vial of gas found in Harry's place can temporarily turn Pokémon into unhinged rage monsters. With help from Lucy, a budding reporter, Tim, and Pikachu track down Harry's sources around Ryme City, hoping to find answers.