As Walter Robinson seeks a way out of the inferno that used to be his house, he remembers a tale told to him long ago by his grandmother about a tunnel connecting the kitchen to the outside smokehouse that was used to hide slaves as they travelled along the underground railway before and during the civil war. As part of the tunnel he finds an area that has been enlarged into a room to hold slaves while they waited for their chance to move on. After stocking the room with basic supplies, such as candles, food and drink he sets out once again to capture Heather, the young girl he believes has been sent by someone from above to help him grow out of the mental state he's always lived in. He captures her after killing her boyfriend and takes her to the room. Heather's mom, bonnie, is determined to find her daughter again and sets out on a search that leads her to the room where she is also taken captive after doing battle with Walter. At every chance they get from then on Heather and Bonnie seek a way out of the hell they're in, attempting and failing more than once before the final battle between Bonnie and Walter begins.