Livey Ell is the only normal person in a family of math geniuses. From her absentminded professor father to her weirdo little brother Darby, it's a wonder she's as normal as she is. But when Darby's imaginary friend Bob turns out to be very real, Livey's life takes a turn for the extraordinary. Bob, a creature of pure math, hates chaos and disorder, and tries to fix it in any way he can. When he turns his attentions on our disorderly world, Livey and Darby must stop him at all costs, before life as we know it is changed forever.