Plot
Shaggy discovers that his uncle Colonel Beauregard has died and left him his country estate, Beauregard Manor, a Southern plantation. He, along with Scooby and Scrappy, head for the estate in order to claim Shaggy's inheritance. Before they can get there, they meet Sheriff Rufus Buzby, who warns them about the estate being haunted and that they should return home. Before he can fully convince them, he receives a call from dispatch, notifying him that a circus train has derailed, resulting in many of the circus animals escaping. Shaggy, Scooby and Scrappy continue driving down an increasingly spooky road which passes through the family cemetery. Along the way, they encounter a Headless Horseman, a ghost wolf, and the alleged ghost of the Colonel who orders them to leave or else.
Having finally arrived at Beauregard Manor, Shaggy, Scooby and Scrappy meet the late Colonel's creepy manservant Farquard, who tells them that a vast fortune in jewels is hidden somewhere on the estate, which he believes is rightfully his and that Shaggy has no business there. Initially, Shaggy wants to leave, but before they can do that, his truck apparently sinks into quicksand, forcing him, Scooby and Scrappy to spend the night there. With ghosts haunting the place, Scrappy has the idea to call a group of ghost exterminators called The Boo Brothers. Surprisingly, the exterminators—Meako, Freako, and Shreako—are themselves ghosts styled after The Three Stooges, who proceed to hunt down the ghosts that are haunting the estate, with little success. In addition, Shaggy meets Sadie Mae Scroggins and her shotgun-toting older brother Billy Bob Scroggins whose family has an old feud with the Beauregard family. After learning that Shaggy is related to the colonel, Sadie falls in love with him and Billy Bob wants to shoot him.
After things calm down a little, Shaggy, Scooby and Scrappy decide to go to the kitchen to eat something, only to find proof that the famous fortune in jewels is real, when they find a diamond ring and a letter from the late Colonel with a clue to a treasure hunt. Intrigued by that very first clue, the gang decides to hunt down the rest of the jewels much to Farquard's chagrin and that of Sheriff Buzby, who drops by to provide a warning about a gorilla that has escaped from the wrecked circus train and was seen headed towards the Beauregard estate. The Sheriff is seemingly skeptical about the jewels' existence.
Shaggy, Scooby and Scrappy follow the trail through a number of clues that the Colonel has hidden for them, which takes them to several different points in the mansion and also in the rest of the plantation. As they progress in their treasure hunt, things become harder, with numerous ghosts appearing, including that of Colonel Beauregard, the Headless Horseman, and a sinister, skeletal Skull Ghost. To make matters worse, they also have to deal with Billy Bob Scroggins and his sister Sadie Mae, both of whom continue to pursue Shaggy, and who keep showing up along with the escaped gorilla. On top of that, the trio encounter a very angry bear, and the Boo Brothers reveal themselves incapable of getting rid of any ghost, only causing more mayhem whenever they try to help. During the search, however, the lost truck is found, having sunk into a secret underground tunnel.
After much treasure hunting, the gang finally find the last clue, revealing that the treasure is hidden in the mansion's fireplace, much to the happiness of the Skull Ghost, who holds the gang at gun point, and tries to claim it for himself before the treasure pours out of the fireplace, trapping the ghost beneath a pile of gold and jewels. Shaggy, Scooby and Scrappy then unmask the Skull Ghost, who appears to be Sheriff Buzby. Just then, however, the real Sheriff Rufus Buzby arrives, revealing that the Skull Ghost is actually his greedy brother, T.J. who had been impersonating him, as well as the remaining ghosts that were haunting the place.
With the treasure found, Shaggy is taken by the Boo Brothers' story that they need a home to haunt, so he turns the mansion over to them and the treasure is put into the Beauregard Trust Fund for Orphans. Saying their goodbyes, Shaggy and the dogs drive back home. Along the way, they encounter once more the ghost of Colonel Beauregard. Shaggy thinks this is another prank by Scooby, until he realizes it's real. He subsequently speeds away as fast as possible.
