The Swan Princess: The Secret of the Castle.It has been one year since the events of The Swan Princess, but Derek and Odette's anniversary is interrupted by the vandalism of Knuckles, minion of the evil sorcerer Clavius. Clavius was the partner friend of Rothbart, villain of the previous film; they conquered the Forbidden Arts together until Rothbart drove Clavius underground after betraying their partnership. Clavius now wants to claim the magical orb of the Forbidden Arts that is located somewhere in Swan Lake castle, which has become Derek and Odette's new home. Clavius has Knuckles perform acts of vandalism in the kingdom that keep Derek busy and make him neglect both Odette and Uberta. On Uberta's birthday, she is abducted by Clavius, who wants to use her as leverage. When Derek sets out to rescue his mother, Clavius sneaks into Swan Lake castle, where he locks Odette in a tower and then goes after the orb himself. Bridget, who was once Rothbart's accomplice but has joined the side of good, recognizes Clavius and knows that he is after the Forbidden Arts. She takes Speed, Puffin, and Jean-Bob into the catacombs under the castle where they find the orb first. After claiming the orb, they race back upstairs and free Odette. Odette knows now that Derek is heading into a trap, but Puffin cannot fly because his tail has been injured by Knuckles, so she convinces Bridget to use the orb to change her into a swan. Once transformed, Odette flies off to warn Derek. Clavius stumbles upon the remaining group and a chase ensues throughout the castle. Clavius eventually obtains the orb, and locks Bridget and the animals in the watery dungeon, although they later escape. Elsewhere, Odette reaches Derek in time to save him from a pit of quicksand. Racing back to the castle, they see Clavius escaping in his hot-air balloon, from which Speed, Puffin and Jean-Bob are secretly clinging to in the hopes of being able to regain the orb. Derek and Odette follow the balloon to Clavius' volcano lair. Knuckles tries to stop them, and after a fight, Knuckles falls into the lava pool beneath the volcano...