A boy named Shō remembers the week in summer he spent at his mother's home with his maternal great aunt, Sadako, and the housemaid, Haru. When Shō arrives, he gets a glimpse of Arrietty, a Borrower girl, returning to her home through an underground air vent.
At night, Arrietty's father, Pod, takes her on her first "borrowing" mission, to get sugar and tissue paper. After obtaining a sugar cube from the kitchen, they travel to a bedroom which they enter through a dollhouse. It is Shō's bedroom; he sees Arrietty when she tries to take a tissue from his table. Startled, she drops the sugar cube. Shō tries to comfort her but Pod and Arrietty leave.