Sally Hurst (Bailee Madison), a lonely, withdrawn child, has just arrived in Rhode Island to live with her father Alex (Guy Pearce) and his new girlfriend Kim (Katie Holmes) at the 19th-century mansion they are restoring. While exploring the sprawling estate, the young girl discovers a hidden basement, undisturbed since the strange disappearance of the mansion's builder a century ago. When Sally unwittingly lets loose a race of ancient, dark-dwelling creatures who conspire to drag her down into the mysterious house’s bottomless depths, she must convince Alex and Kim that it’s not a fantasy—before the evil lurking in the dark consumes them all.