Upon being sent to live with relatives in the countryside due to an illness, an emotionally distant adolescent girl becomes obsessed with an abandoned mansion and infatuated with a girl who lives there - a girl who may or may not be real.

14-year-old Arrietty and the rest of the Clock family live in peaceful anonymity as they make their own home from items "borrowed" from the house's human inhabitants. However, life changes for the Clocks when a human boy discovers Arrietty.