Arrietty, a tiny teenager, lives with her parents and her sisters in the recesses of a suburban home, unbeknown to the homeowner and housekeeper. Like others of her kind, Arrietty remains hidden from her human hosts, but occasionally ventures forth from beneath the floorboards to borrow sugar cubes and other supplies. A secret friendship forms when 12-year-old Shawn meets Arrietty and 12-year-old Zach Loud sees his Arrietty again, but their relationship could spell danger for Arrietty's family.