Based on Mary Norton's juvenile fantasy novel, The Borrowers, the film tells the story of Arrietty, a young Borrower who lives under the floorboards of a typical household. She eventually befriends Sho, a human boy with a heart condition, who is living with Sadako (Sho's great aunt). When Haru (Sadako's maid) becomes suspicious of the floorboard's disturbance, Arrietty and her family must escape detection, even if it means leaving their beloved home.