Five years after an unexplained malfunction causes the death of 15 tour-goers and staff on the opening night of a Halloween haunted house tour (Hell House), a documentary film crew visits the scene of the tragedy to investigate what really happened that night.

Set one year after the events of Hell House LLC II, the hotel is on the verge of being torn down when it is purchased by billionaire Russell Wynn as the new home for his popular interactive show, Insomnia. He invites journalist Venessa Sheppard and her crew to record everything happening inside the hotel leading up to the performance - but they soon encounter a more nefarious plot, one that threatens to unleash a veritable hell on earth.