Alison and Robert visit a prison after a series of mysterious suicides take place behind bars. There they encounter a serial killer, who blames a malevolent spirit called the Rat Man on his own murderous spree. As Alison strives to banish the evil from the place to help the other convicts, she puts herself in terrible danger.

• Stephen Volk

• Nikki Amuka-Bird
• Andrew Lincoln
• Harry Treadaway