Mallory is in Washington, D. C. with her fourth grade class. She can't wait to see the famous monuments and museums. But from the moment she sets foot in the nation's capital, there's one thing she doesn't see much of...her best friend. Mary Ann is spending so much time with the new boy in their class, she's forgotten all about being partners with Mallory. And when Mallory wanders off to wiggle her loose tooth, her tooth isn't the only thing that is lost! Will Mallory's trip to Washington turn out to be one she'll always remember or something she'd rather forget?