Beneath the floorboards of a country manor lives Arrietty, a daring ten-centimetre-tall girl who lives with her family in absolute secrecy. Their most sacred rule is never to be seen by humans, but everything changes when young Sho, a boy in fragile health who is staying temporarily at the house, accidentally discovers her. Despite the dangers and prejudices they face, a deep and sincere friendship grows between them. However, this unexpected discovery puts the peaceful existence of the Borrowers at risk, and they must face great threats to protect their home and ensure their survival.