The first episode of the series' rebooted sequel.
After being jailed by Sheriff Bronson Stone for solving another mystery, the Mystery Inc. gang stumbles upon yet another mystery: A slime mutant that lives underneath the town is cocooning anyone who gets in its way. They follow the monster to the Crystal Cove caves where they find a magnifying glass-shaped locket and cocooned bodies of construction workers. Despite being warned not to continue investigating by their parents and authority figures, they steal one of the bodies and bring it to Professor Emmanuel Raffalo for studying. Meanwhile, Velma is trying to get Shaggy to be more intimate in their relationship while Shaggy is not yet ready to tell Scooby. Daphne keeps hinting her romantic feelings towards Fred who is oblivious to almost everything apart from solving mysteries and building traps. After the disappearance of Professor Raffalo, the gang discovers that cocooned material are made from the same material as Fruitmeir's Dessert, a new dessert bar that opened two months ago. Shaggy and Scooby infiltrate Fruitmeir's by posing as female servers, and Daphne stumbles across a hole that leads to the caves which go right under the bank. Although not as planned, they catch the monster just as Mayor Jones and Sheriff Stone arrive. When the kids state that Franklin Fruitmeir was the monster, Franklin then shows up. The Slime Monster is actually revealed to be Professor Raffalo, who discovered the caves while collecting mold spores and found out it led to the bank, so he posed as the Slime Mutant using Fruitmeir's Dessert and staged his own disappearance to lower any suspicion and frame Franklin. When Daphne shows him the locket she found in the caves, Mayor Jones seems suspicious, but Raffalo claims to know nothing about the locket as he is taken away. Sheriff Stone states that despite the fact that the town lost a stream of revenue, he actually thanks the kids for preventing an attempted bank robbery. Later that night, the gang is contacted by a mysterious man called Mr. E who says they have uncovered "a truth that should have remained buried" and that "the real mystery has just begun".
- Frank Welker - Scooby Doo, Fred Jones, Barty Blake,
- Grey Delisle - Daphne Blake, Paula Rogers, additional voices
- Matthew Lillard - Norville "Shaggy" Rogers
- Mindy Cohn - Velma Dinkley
- Kevin Dunn - Dale Dinkley, Workman #1
- Patrick Warburton - Sheriff Bronson Stone
- Dee Bradley Baker - Slime Mutant, Franklin Fruitmeir
- Jeff Bennett - Professor Raffalo, Male Tourist
- Gary Cole - Mayor Fred Jones Sr., Foreman
- Vivica A. Fox - Angel Dynamite
- Fred Tatasciore - Workman #2
- Lewis Black - Mr. E
- Casey Kasem - Coleman Rogers
- Kath Soucie - Nan Blake