The gang is driving to New England. Shaggy's uncle has inherited the old King Arthur castle and sent it to New England stone by stone. When they get it there, something is wrong. They learn that he's also brought back the ghosts of Merlin and the Black Knight.
Fred, Daphne, Velma, Scooby and Shaggy head to New England to visit Shaggy's uncle, Shagworthy. On the way, they stop at a magician's, Zarko, magic show. He invites Shaggy and Scooby up onto stage and "saws them in half" the old magic box trick. However, Shaggy and Scooby get so scared at this trick that they run while the other half runs the other way. Both halves of the box crash and the audience boos. Zarko gets mad at Scooby and Shaggy for ruining his act and they run away. The gang leaves and head for Uncle Shagworthy's castle. Upon arrival, they are greeted by a man named Clarence who says he is the caretaker who warns them away from the castle. He explains when Shagworthy bought the castle, the Curse of Camelot came along with it. The caretaker tells Mystery Inc. that the castle is haunted by Merlin the wizard and his evil slave, the Black Knight. He also tells them Shagworthy has gone missing. Soon after, Merlin and the Black Knight appears, warns the kids away, and kidnaps the caretaker.
The five sleuths enter the castle and begin looking for Shagworthy. They begin walking through the winding corridors. The Black Knight appears, and the gang runs into a secret room with a replica of King Arthur and the Knights of the Round Table in it. All of a sudden, flying ghostly figures rise up from the knight statues and chase the gang. Shaggy and Scooby get caught by Merlin and the Knight and get hypnotized to dispose of Fred, Daphne and Velma. Meanwhile, Fred, Velma and Daphne hide in the library where they find signs of a struggle, and a red silk scarf. Shaggy and Scooby try dropping a chandelier on Fred and the girls but it backfires, and Fred, Daphne and Velma manage to get them out of their trance with Scooby Snacks. Scooby or Shaggy has no memory of the events.
The gang keeps looking for Shagworthy through the spooky castle. They go down into the dungeon where they find Shagworthy chained up on the wall. Shagworthy explains that Merlin and the knight started appearing in the castle every night at 12:15. The gang is puzzled at the odd time, but they continue looking for clues. They go to the treasure room to find it has been ransacked. Before they can go any further, the flying ghost knights appear and chase Fred, Daphne and Velma. Scooby and Shaggy are pursued by the Knight and Merlin. They fool them by pretending to be corny salesman, and then hide in suits of armor. Fred, Daphne and Velma hide in the music room, where they hear the Knight approaching. They trap him, to find it was Scooby and Shaggy in the knight costume.
The gang searches the tower and finds an electronic organ. Velma is starting to piece the puzzle together. Now, all they have to do is trap the wizard and his tin friend. Scooby and Shaggy act as bait, and lure the two ghosts to their trap, but it backfires and Scooby and Shaggy flee, but manage to trap Merlin and the Knight in a woven tapestry. Merlin is unmasked as Clarence the caretaker and the Knight is unmasked as a hired henchman. But Velma isn't so sure; she pulls off a rubber mask to reveal the caretaker was a disguise; Zarko is the culprit! He disguised himself as the caretaker. Mystery Inc. explains it all. Their first clue was when the knight carried the caretaker off through a wall, revealed by Velma to be a common magician trick. The silk scarf was a common tool used by magicians for some tricks. All of the flying ghost knights were controlled by pushing keys on the organ; they were just magician illusions. Zarko wanted to scare everyone off so he could search for Shagworthy's jewels. Also, Shagworthy told them about Merlin appearing at 12:15. Zarko's show ended at midnight and it took 15 minutes to get to the castle. Zarko and his henchman were presumably arrested.
Shagworthy offers Scooby and Shaggy a banquet. He tells Fred, Daphne, and Velma that he keeps the jewels in the refrigerator which are inside the buckets.
Cast and characters
|Don Messick|| Scooby-Doo|
|Casey Kasem|| Shaggy Rogers|
|Frank Welker|| Fred Jones|
|Heather North||Daphne Blake|
|Patricia Stevens||Velma Dinkley|
|John Stephenson|| Zarko the Magician|
Ghost of Merlin
- Ghost of Merlin/Zarko
- Black Knight/Zarko's henchman
| Zarko as Clarence and the Ghost of Merlin|
His henchman as the Black Knight
|To find and steal Shagworthy's jewels.|
- It can be assumed that Shaggy's family (and Scooby's as well) is wealthy. Shaggy's Uncle Nat live in a large estate in rural Massachussetts (The Lochness Mess), his Uncle Shagworth managed to bring an old English castle to the U.S. in this episode and Shaggy's parents also live in a large estate (as seen in the episode Wedding Bell Boos!).
- Shaggy and Scooby are hypnotized for a second time. Apparently, mind control may turn them "evil" but it cannot eliminate their goofy, over-the-top personalities.
- This is the second time, that the villain is called Black Knight, the first was in the original Scooby-Doo, Where Are You! episode, What a Night for a Knight.
Animation mistakes and/or technical glitches
- In one shot, Velma's eyes are missing.
Inconsistencies/continuity errors and/or goofs/oddities
- It is never explained why the Ghost of Merlin is evil (after all the real Merlin was advisor to King Arthur a good king).
- For the trap, Shaggy and Scooby act as bait whilst Fred, Velma and Daphne remain in the separate tower to operate the magic organ. However, when the plan goofs and the villains are trapped by a fallen tapestry, the other three are just seconds away.
- It was never explained how the Black Knight made Clarance (a.k.a. Zarko) disappear with the Ghost of Merlin there (since it is revealed that Clarence/Zarko was Merlin). Third henchmen maybe? Illusion? Hologram?
- The Scooby-Doo!/Dynomutt Hour: The Complete Series DVD set released March 7, 2006.
- Scooby-Doo! 13 Spooky Tales: Run for Your 'Rife! compilation DVD set released September 10, 2013.
The Headless Horseman of Halloween
The Harum-Scarum Sanitarium