The first incarnation of what has become a franchise-of-sorts, Scooby-Doo is a large, loveable but cowardly Great Dane who hangs around four California high school students (Fred, Velma, Daphne and Shaggy). The four teen-agers are in constant search of mysteries and adventures, driving around in a bright green van known as the Mystery Machine. Many of the group's adventures involve villians who take on supernatural disguises (ghosts and monsters); the villians' activities usually involve blackmail, theft, fraud and other forms of corruption.
While driving back from the movies, the gang finds a strange man in the back of the Mystery Machine. They recognize it as the ghost of Mr. Hyde who is a jewel thief. They follow him to a house where they meet a descendent of Dr. Jekyll who claims to be the ghost of Hyde, but is he telling the truth?
While in China, the gang pursues an ancient Chinese mask at an antique show. Soon strange things start happening. The gang is pursued by some horrible ghosts. They learn that the ghost of long dead emperor has returned to claim what is rightfully his. Things take a serious turn when Daphne is taken hostage.
While driving to the barnyard dance, the gang finds an injured bank guard. He gives them a blank paper and says something about a flame. The gang learns of a local bank robber called the Creeper. Things take a serious turn when the Creeper tries to steal the blank paper.
While fishing, the gang encounters a frozen caveman. The gang takes it Ocean Land to keep it in the cooler but someone melts the ice and now the caveman is on the loose.
While driving to a concert, the gang gets lost. A strange man with a lantern tells them to avoid taking a right fork in the road. That would take them to a mansion that's rumored to be haunted by a headless man.
Scooby and Shaggy are having a fun time in Hawaii with their guide John Simms. Things take a serious turn when a voodoo witch doctor shows up and Simms mysteriously vanishes.
While camping out in the woods, the gang comes across a tombstone of a man that was a werewolf. Are they pursuing the ghost of a werewolf?
The gang is having fun at a TV station with their friend Johnny but then a wax creature shows up. Johnny tells them that years ago a wax maker named Grisby used to work for the station. He was fired and threatened to bring one of his wax creations to life to seek revenge on the people who fired him.