It's Christmas Eve, and there's a big party. Young Clara gets a special present, a nutcracker. At midnight, the Christmas tree grows magically, and the Nutcracker springs to life, doing battle with an army of mice. It's Act One of "The Nutcracker," by Peter Tchaikovsky. Conductor Simon Rattle says that the more he listened to Tchaikovsky's masterpiece, the more fascinated he became by it. Today, Rattle and the Berlin Philharmonic perform Act One of Tchaikovsky's "Nutcracker." And they'll be back on Monday's show for Act Two.