Shaggy's uncle disappears and leaves Shaggy with millions of dollars, so Shaggy and Scooby-Doo go to the mansion he left for them and start exploring. They see some of his inventions and then Shaggy sees a note about how his new invention is trying to be stolen by someone and now he must go into hiding. Now Scooby and Shaggy have to go and solve another mystery.

Shaggy and Scooby meet up with Fred, Velma, and Daphne at a military base where Dr. Phibes' agents use their new invisible technology to steal weapons.