Eight-year-old Sally Hurst (Bailee Madison) has been shipped off to live with her father Alex (Pearce) and his girlfriend Kim (Katie Holmes) in their underconstruction Gothic mansion.
To help her sleep, Sally is given a musical nightlight, but its melody only awakens a horde of terrifying, otherworldly creatures living beneath the house.
Despite the warnings of workman Mr Harris (Jack Thompson), Sally ventures into the basement where she can hear someone - or something - calling her name. As the creatures escape, wounding Harris, it's clear they have evil intentions and are ultimately after young Sally.