In the movie, Scooby-Doo, Shaggy, Velma, Daphne, and Fred find themselves transported back to medieval times through a magical portal created by the evil sorceress, Morgana Le Fay. They soon discover that they are in the land of King Arthur and his Knights of the Round Table, where they are pursued by dragons, enchanted forests, and treacherous knights.
As they try to find their way back home, the gang encounters a host of characters from Arthurian legend, including Merlin the Magician and the elusive Lady of the Lake. But their greatest challenge comes in the form of Morgana, who is determined to use their time-traveling abilities to gain the powerful Excalibur sword and take over the kingdom.
With the help of their new friends, the gang must use their modern technology and investigative skills to outwit Morgana and her minions, while also learning the importance of bravery, chivalry, and honor. Will they be able to defeat Morgana and return to their own time, or will they be stuck in the age of knights and dragons forever?