The snowmen are getting their Halloween costumes ready for the latest picture book in this New York Times bestselling series.

Have you ever built a snowman and discovered the next day that his grin has gotten a little crooked, or his tree-branch arms have moved? And you've wondered . . . what do snowmen do when we're not watching?

After an early snowfall, a few kids build some snowmen before going trick-or-treating. And when the kids go off to bed, the snowmen have their own Halloween festival! There's candy and apple-bobbing and costume contests and all sorts of autumn activities. When the kids wake up the next morning, the snowmen are gone... but they've left a very special message behind.