Team Powerpuff and Mystery Inc. travel to Oakhaven, Massachusetts, where they meet Velma and Lucy's favorite horror writer, Ben Ravencroft, and reunite with the Loud kids' old friend, Gizmo. They must solve a mystery involving Ben's descendant, Sarah Ravencroft, who happens to be a witch.
The Powerpuff Girls: Blossom, Bubbles & Buttercup
The Loud Kids: Lincoln, Lori, Leni, Luna, Luan, Lynn, Lucy, Lola, Lana, Lisa & Lily
Mystery Inc.: Scooby-Doo, Shaggy, Fred, Daphne & Velma