Little Mystery on Swan Lake
Having once been allied with the evil Rothbart, Zelda an equally evil sorceress plans to cause chaos in the peaceful land of Swan Lake by stealing the Forbidden Arts, a treasure which gives the owner unlimited power. Zelda's plans involve using a Yakey-bird to infiltrate the castle and then to kidnap Odette, holding her to ransom for the Forbidden Arts. It leads Derek into yet another showdown with a sorceress.
So it should be obvious but I had better state it "The Swan Princess: The Mystery of the Enchanted Treasure" is a children's movie and only a children's movie, it is not made for any adult who found the first "The Swan Princess" entertaining. I say that because this third "The Swan Princess" movie is weak for adults and not wanting to sound cruel feels like a movie going through the motions rather than doing something new and original. Basically it is made for the sort of audience who will enjoy the funny voices, the animated characters and the musical interludes but won't pay a great deal of attention to the detail and there is nothing wrong with that.
The thing is that because "The Swan Princess: The Mystery of the Enchanted Treasure" is only doing what it had done before there isn't a lot to say about it. Yes some of it is still fun and there are a handful of reasonably amusing jokes in there but for the most this is the movie which if you were to watch with a child will play out in front of your eyes whilst you're thinking about other things and then suddenly will be over.
What this all boils down to is that if you have young children they might enjoy "The Swan Princess: The Mystery of the Enchanted Treasure" as it is simple entertainment. But if as a grown up you enjoyed "The Swan Princess" this third movie doesn't offer you a great deal as it frequently feels like it is just covering old ground again.