Lewis Barnavelt (played by Owen Vaccaro) is a young boy whose parents have just died in a car accident. He's sent to live with his eccentric uncle Jonathan (Jack Black - happily not quite as over-the-top as usual) - who turns out to be a warlock, living in a house with a sinister clock ticking in the walls. Their next door neighbour is Florence Zimmerman (Cate Blanchett), who is a witch and a good friend of Jonathan's. Lewis struggles with his grief, starting at a new school, and - like Jonathan and Florence - starts to worry about what exactly the clock is going to do when its countdown ends. He also starts training as a warlock himself.
Black and Blanchett seem to be having an absolutely marvelous time in the movie, and I really enjoyed the sense of whimsy in most scenes. It reminded me considerably of "The Sorcerer's Apprentice" - another flawed and goofy movie that was nevertheless charming and entertaining.