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, a documentary crew travels back to the scene of the tragedy to find out what really happened.

Eight years after the opening night tragedy of HELL HOUSE LLC, many unanswered questions remain. Thanks to an anonymous tip, an investigative journalist is convinced that key evidence is hidden inside the abandoned Abaddon Hotel. She assembles a team to break into the hotel in hopes of discovering the truth. But the source of the tip and the secrets of the Abaddon Hotel are more horrifying than any of them could have imagined.

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.

A group of cold case investigators stay at the Carmichael Manor, site of the grisly and unsolved murders of the Carmichael family back in the eighties. After four nights, the group was never heard from again. What is discovered on their footage is even more disturbing than anything found on the Hell House tapes.

After a near-death experience, Vanessa Shepherd faces nightmares in Abaddon. As mysterious deaths occur around her, she discovers her connection to the Abaddon Hotel, Carmichael Manor, and decades of unexplained murders.