Scooby is named as one of the heirs of the late Colonel Beauregard Sanders, whom he had rescued from a fish pond several years before. As a condition for inheriting an equal share of $1,000,000, the heirs must spend the night in the Sanders family mansion—which is haunted.While bathing, Scooby is whisked through a trapdoor and into the coal cellar, where he is menaced by a shadowy, chain-rattling phantom. He escapes, but no one believes his story until the same phantom appears at midnight and spirits Cousin Simple away. The gang rigs up a Scooby dummy to fool the phantom, but Shaggy, Scooby and Velma wind up in a secret cave under the mansion. After being menaced by a flying Confederate uniform, the three find a secret elevator which takes them to Cousin Slicker's room—and they find that Cousin Slicker and the rest of the cousins have vanished.
Following the sound of an organ playing, the gang becomes trapped in the music room (and are briefly threatened when the walls begin to close in); they decipher a musical riddle, opening a trapdoor which leads to underground catacombs in which they find five coffins, four of them filled with the missing cousins. The phantom shadow, now manifesting itself as two green ghosts, appears and chases the gang.
After giving the ghosts the slip, the gang regroups and constructs a trap using a fan, a spring-loaded ironing board, and a washing machine. But when Scooby throws the fan switch the wrong way, the entire contraption goes airborne. However, they still manage to catch the ghosts, unmasked as attorneys Creeps and Crawls, who were trying to keep control of the Sanders fortune. Not that it would have done them any good, as it turns out to be $1,000,000 in worthless Confederate money.
- Beaureguard name Appears in Scooby Doo Show episode with the Gator Ghoul as a movie production incorporation; also the name appears in Scooby-Doo meets the Boo Brothers as a ghost (Shaggy's Uncle)