Something has gone terribly wrong in the magical kingdom of Narnia. The new film adaptation of C.S. Lewis's classic 'The Lion, the Witch and the Wardrobe' was a moderately well-received charmer; 'Prince Caspian' showed diminishing returns; and 'Voyage of the Dawn Treader', judging by the reviews and last weekend's dismal box office returns, was not a movie anyone much wanted. What happened? Why did this eagerly awaited film franchise turn into such a bust, and how did American audiences so quickly lose interest?

I want to suggest that the 'Narnia' films, the third one in particular, fail as works of fantasy. They don't know what to do with magic, which is, after all, Narnia's defining characteristic. To see why this is, it's useful to compare 'Narnia' to 'Harry Potter', a more recent classic that has spawned a far better and more successful movie series.

In 'Harry Potter', magic is hard. It's both an art and a science. The characters spend years training to master it and bend it to their will; some never succeed. There are rules. Things go wrong: spells don't work as expected; potions have flaws and unpleasant side effects. In this universe, magic is more than a series of impossible things happening at the random behest of the plot. It means something; it has structure, and it gives the movies structure too.