The show opens with Vincent VanGhoul talking about how he saw someone through his crystal ball opening the Demon Chest and releasing the 13 ghosts of Scooby-Doo.
Inside a temple in the Himalayas, Bogel is taking a shower and hears a loud noise. He wakes Weerd and tells him about it, and then they hear the noise again. Weerd says it's the 13 ghosts inside the Chest and that they want out. Weerd says they're going to help them get out, but Bogel doesn't understand, saying those are the meanest ghosts on Earth. Weerd then says that if they let the ghosts out, they'll appreciate their help. Bogel says they can't open the Chest because they're ghosts, and only living ones can open it. Weerd says the Chest is signaling that living ones are near, and that they're really stupid so they'll open the Chest.
Shaggy, flying the "Mystery Flying Machine," thinks they've arrived in Hawaii, but Daphne points out that they're actually in the Himalayas, because Scooby had a map to the Himalayas instead of one to Hawaii.
Weerd uses magic to make the plane's gas tank empty and the plane starts to crash. Shaggy and Scooby try to parachute out of the plane but things go awry and they end up hanging from the back of the plane by their parachutes. Daphne tries to land the plane with Scrappy-Doo.
A young boy named Flim Flam is running from townsfolk, in a town by the castle in the Himalayas. The townsfolk surround him and tell him to leave town, telling him all he's done is cause trouble. He unsuccessfully tries to sell them Lotsa Luck Joy Juice. Then the plane crashes into town and Flim Flam grabs on to Scooby's parachute to get away from the townspeople. The plane stops right outside the temple. Flim Flam introduces himself. Then a cop comes and says everyone is in trouble. Weerd and Bogel see the Scooby Gang has landed and plan to steal their plane.
Now in court, the Gang faces a judge. The judge gruffly tells the Gang they need to be out of town by sunset.
Returning to the temple, the Gang sees their plane has disappeared. Daphne points out that the plane was dragged inside the temple. They try to get in but the door is locked. Bogel actually locked the door by mistake, which makes Weerd mad. Flim Flam says he knows a mystic who can help the Gang get into the temple, so they go off to see him.
The Gang goes into a pub, getting weird looks from all the townsfolk. They go into the back room and meet Vincent VanGhoul, who Flim Flam introduces as the "mystic wonder of the Universe". Daphne asks where their airplane is, and Vincent says it's in the temple, but they shouldn't go in because evil spirits are there. He says those spirits put a curse on the town that turns them into werewolves every night.
Eavesdropping, some of the townsfolk find out that the Gang now knows their secret and they decide the Gang can never leave. The townsfolk try to keep the Gang in the pub, serving them food and Wolfbane. Ghoulio sings on stage. Daphne drinks some Wolfbane, but Scrappy says that's what turns people into werewolves. The Gang tries to leave, but only Flim Flam and Scrappy get out. The townsfolk turn into werewolves, and so does Daphne. They almost capture Shaggy and Scooby, but they knock down the door just in time and run away. They jump into a sewer where Flim Flam and Scrappy are hiding, and were-Daphne follows them. Flim Flam cures here with some of his Lotsa Luck Joy Juice, and everyone is surprised it actually worked.
Bogel and Weerd are drilling a hole in the temple's door so the Gang can get in. Shaggy and Scooby don't want to go in, but when they see the werewolves are right behind them, they go in along with the others. Everyone piles rocks in front of the whole to block the werewolves, but they break through and start chasing everyone. Weerd and Bogel think Shaggy and Scooby look the most stupid and lead them down to the crypt where the Chest is.
Flim Flam cures the townsfolk with some Lotsa Luck Joy Juice, which he then starts selling to everyone. The townsfolk thank the Gang. Daphne asks how the curse came about, and the townsfolk say that a long time ago they captured the 13 most hideous ghosts in the world and put them in a chest in the temple's crypt. Before the chest was closed though, the ghosts placed a curse on the townsfolk that would turn them into werewolves every night. That's why the townsfolk tried to scare off the gang - so they wouldn't find out the awful truth. Daphne asks where their plane is, but the townsfolk have no idea.
Shaggy and Scooby are downstairs, looking for an exit. They find the game show "Let$ Make Em $queal" underway, as the host "Haunty Mall" (Weerd) approaches them. He asks them which prize they'd like to pick - their airplane, a doggie dream house, or what's in the box. Weerd says that what's in the box is amazing and will take their breath away. The audience shouts for them to pick the box.
Daphne, Scrappy, and Flim Flam still can't find their plan, so Flim Flam calls Vincent to help. He says it's in the crypt and was taken there by two spirits, whose only goal is to lure the living down there to open the Chest. He says that fortunately, only a complete fool would ever open that box. This reminds Daphne that Scooby and Shaggy are still missing.
The faux-game show returns and Weerd asks what prize Scooby and Shaggy want. They decide on the box, and Shaggy says it's because they both had a "dumb hunch". The rest of the gang tries to stop Scooby and Shaggy from opening the box but they're too late and the ghosts escape, blasting out of the temple and into the sky. Vincent says that the ghosts must be returned to the chest by Scooby and Shaggy, because they're the only ones who can recapture them. He says that the Gang will need his help and he gives them a crystal to contact him with. Flim Flam joins the team, and says he filled up the plane with Lotsa Luck Joy Juice so they can leave. The plane flies away, with Weerd and Bogel sitting on top of it.