A group of young urban explorers and a private military unit could become the final pieces in a 60-year plan to reopen a door that should have stayed closed. But what they unleashed could almost tear our world apart.

The year is 1955. NATO and the Allied Forces have been conducting secret, occult experiments in a bid to win the Arms Race. Now, they have finally succeeded but what the Army has unleashed threatens to tear our world apart. One woman must lead the only survivors past horrors that the military has no way to control - and fight to close what should never have been opened.

During a handover to the head of counter-terrorism of MI5, Harry Pearce, a terrorist escapes custody. When Harry disappears soon after, his protégé is tasked with finding out what happened as an impending attack on London looms, and eventually uncovers a deadly conspiracy.

Haunted by terrible waking nightmares, Joan must face more than just her own fears as she is stalked by a murderous sociopath, haunted by one of his victims, and terrorized by The Beast, a relentless and horrifying spirit of vengeance which never sleeps.

Hannah plays DI Jack Cloth, who is called in to investigate an apparent series of serial killings alongside his new partner, DC Anne Oldman, described as a "plucky, no-nonsense sidekick". Playing with the cliches and conventions of British police dramas, subplots include Cloth dealing with visions of his dead wife and the bisexual DC Oldman coming to grips with her feelings for both her female fiancee and Cloth.