The Mystery Gang travels to San De Pedro, California for the Mega Mondo Pop! Comic ConApaloosa, where Shaggy Rogers [Matthew Lillard] and Scooby-Doo [Frank Welker] enter a costume contest as their favorite comic book heroes, the Blue Falcon and Dynomutt [Frank Welker]. There, they meet Jennifer Severin [Nika Futterman], a movie producer in the middle of making a dark and gritty Blue Falcon movie; the film’s leading actor Brad Adams [Diedrich Bader]; Hank Prince [Gregg Berger], the owner of a comic book store that Shaggy frequents; his nephew Austin [Tara Strong]; Owen Garrison [Jeff Bennett], the washed-up star of the original Blue Falcon television series; and Jack Rabble [Fred Tatasciore], a former BattleBots champion. When Shaggy Rogers [Matthew Lillard] and Scooby-Doo [Frank Welker] try to get Owen Garrison’s autograph, the veteran entertainer vents about Severin’s studio erasing all trace of his beloved series, hinting at a grudge simmering beneath the surface. In the middle of a screening for the movie’s trailer, Mr. Hyde [John DiMaggio], a villain from the Blue Falcon television days, bursts in to terrorize the convention.
As the Mystery Gang offers to investigate, most attendees point to Garrison as the likely culprit, but Shaggy Rogers [Matthew Lillard] and Scooby-Doo [Frank Welker] refuse to accept that verdict. They review surveillance footage and uncover a troubling motive: Severin stands to gain amplified publicity for her movie from the chaos, while Brad Adams [Diedrich Bader] resents his role and dares to hope the spectacle will help him walk away from the production. The clues reveal that Hyde’s attacks draw directly from episodes of the old Blue Falcon show, and that the next assault will involve a mutagenic ooze capable of turning living beings into monsters. Frightened and humiliated, the duo retreat to a storage room, where they discover Hyde’s hidden lair before he overtakes the city with a harmless placebo of the ooze. The attack leaves San De Pedro reeling and prompts the mayor to strike: Ron Starlin [Kevin Michael Richardson] fires the Mystery Gang and revokes their access to the convention.
With the Blue Falcon movie premiere scheduled at the local ballpark, Shaggy Rogers [Matthew Lillard], Scooby-Doo [Frank Welker], and their friends plot a bold move. Fred Jones [Frank Welker], Daphne Blake [Grey DeLisle], Velma Dinkley [Mindy Cohn], along with Austin [Tara Strong] and Jack Rabble [Fred Tatasciore], sneak past security to infiltrate Hyde’s lair and put a stop to the threat. They learn that Hyde had been quietly watching the convention and the stadium, preparing for a massive assault, while a colossal Hyde rampages through the arena. Meanwhile, Shaggy and Scooby, trapped inside the stadium, manage to find a way out and rescue Austin from danger, and their friends soon converge to confront the monster. The showdown culminates in a dramatic moment where the towering Hyde is revealed to be a mech seemingly piloted by Owen Garrison, who claims he was framed, though the truth remains to be seen. Scooby-Doo foils a robber attempting to hijack an armored car, and the tide shifts as Garrison, donning his old Blue Falcon costume, joins Scooby to take down the villain once and for all.
The villainy is unmasked: Jack Rabble is Hyde, driven by a desire for revenge after being ousted from BattleBots and forced to monetize conventions. He confesses that the attack was a scheme to divert the convention’s entrance fees into his own pocket, leveraging the chaos to escape with cash while pinning the blame on others. Mayor Starlin arrives to acknowledge his misjudgment, apologizes to the Mystery Gang, and restores their access to the convention. In the aftermath, Severin is impressed by the team’s resilience and commissions a sequel to the Blue Falcon movie, with Owen Garrison appearing as the father of Adams’ character and Scooby serving as Dynomutt once again, signaling a brighter, more collaborative future for the franchise.
