Moxie Fleece knows the rules and follows them--that is, until the day she opens her front door to a mysterious stranger. Suddenly Moxie is involved in Boston's biggest unsolved mystery: The Isabella Stewart Gardner Museum art heist. Moxie has two weeks to find the art, otherwise she and the people she loves will be in big-time danger.

Her tools? Her best friend, Ollie, a geocaching addict who loves to find stuff; her Alzheimer's suffering grandfather, Grumps, who knows lots more than he lets on; and a geometry proof that she sets up to sort out the clues.

It's a race against the clock through downtown Boston as Moxie and Ollie break every rule she's ever lived by to find the art and save her family.