A series of children's fantasy books by Mary Norton (who also wrote Bedknob and Broomstick). Arrietty Clock lives with her parents under the floor in the house of a "human bean". They live by "borrowing" from the human beans (it's only "stealing" if you take things from another Borrower), but never anything that might be missed; a Borrower must never be seen by a human bean, or let a human bean in any way know they exist. Unfortunately, Arrietty is a little too curious for her own good, and ends up talking with a human boy. The boy ends up fetching little things that might help the Borrowers, things they couldn't get for themselves.