While in Ecruteak City, Ash and co notice something wrong with the atmosphere. Apparently Team Rocket stole the crystal bells from the new Tin Tower and Jessie breaks one of them, resulting in harmony being destroyed. What can Ash and co. do about this, and who is the mysterious man with Morty?
Eusine, a character from Pokémon Crystal, makes his debut in the anime.
The title is a reference to "For Whom The Bell Tolls", the book by Ernest Hemingway or the song by Metallica.