After almost six months in Maryland, fifth-grader Oliver still misses his friends back in New Jersey. But things start to change one day, when his neighbor--and possible new friend--Sam lends Oliver a magic hat that takes him back to the 18th- and 19th-century world of Thomas Jefferson. Oliver and his sisters--Cassie, the nice one, and Ruby, the annoying one--end up learning more about Jefferson than they'd expected. And Oliver finds that his new...