After 52 years of solving mysteries, the Scooby gang reunite at Warner Bros. Studios to reminisce about their favorite cases and how they were filmed. But it turns out that the back lot may have its OWN monster problem. Fred, Daphne, Velma, Shaggy, and Scooby-Doo investigate this mystery while celebrating the legacy of the franchise. The Scooby Gang ends up investigating a mystery when they gather to reminisce about their favorite cases.