the people under the stairs (1991)

aka Wes Craven's The People Under the Stairs.
"Leave them alone. I've heard things about them, bad things."
A young boy nicknamed Fool (Brandon Quintin Adams) is persuaded to help burgle his landlord's house. Once inside he becomes trapped when the landlords (Everett McGill and Wendy Robie) return. Hiding in the rambling house, he finds they are keeping kidnapped boys there and when he befriends their daughter Alice (A.J. Langer), he finds out about the true horror inflicted on the children. He becomes determined to rescue them and expose the landlords and their wicked practices, helped by Alice and a boy who lives in the wall space Roach (Sean Whalen).
A nicely realised film full of suspence, with the odd bit of black humour as release.