Case History: At the university's archeology department, the gang is helping a professor put together a display centering on the mummy of Ankha, a three-thousand-year-old relic with a curse on it: Ankha had sworn to come back to life and turn to stone any who disturbed his tomb. Returning from the malt shop, where they had gone to pick up some sandwiches, they find that the mummy is missing and the professor has been petrified. They split up to search for the missing mummy.

But the mummy finds Velma, Shaggy and Scooby first, cornering them and demanding the return of an ancient Egyptian coin which Shaggy had earlier accidentally pocketed. They escape after Scooby nails one of its loose bandages to the floor. Meanwhile, Fred and Daphne have found the professor's colleague, Dr. Najib, turned to stone in his car. The other three return to where they left the mummy; it has broken free but left behind a scrap of his bandages. They go to the lab to test it (it doesn't seem to be three thousand years old) but the mummy appears. Velma and Shaggy escape, but the mummy gets Scooby; the rest of the gang later find a petrified Scooby. But, in fact, the stone Scooby is a fake and Scooby soon shows up.

Returning to the professor's office, the gang researches his notes, which show that Ankha was renowned for his wealth. They also show a picture of a statue that bears a design exactly like that of the coin which the mummy is trying to get. The mummy appears and chases them into the woodshop, where they are attacked by a powersaw that Daphne accidentally turns on. The saw cuts a hole in the floor, knocking them into the gym pool. Fleeing again from the mummy, Shaggy and Scooby find quick-drying cement and spray molds before being bricked up in a shed, inside of which they find the professor, tied up and gagged. Scooby and Shaggy break out of the shed with a power mower, which goes out of control and catches up the mummy. The mummy winds up trapped in the gym basketball goal, where he is unmasked as Dr. Najib. The coin is the key to a secret compartment in a statue containing a priceless diamond scarab. Najib was after the scarab and was using the legend of Ankha to cover up his attempt to steal the artifact.

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