When a series of prison suicides seem to have a supernatural cause, Robert and Alison try to help. Among the inmates they meet serial murderer Ian Garland (David Threlfall - Shameless). He thinks he has found a kindred spirit in Alison and delights in telling her all about the Rat Man, the malevolent spirit who urges him to commit his horrendous crimes. Realising that Garland is responsible for the evil presence in the prison, Alison tries to rid him of the Rat Man, to help the spirit pass over and leave the prisoners in peace. But as she does so, Alison places herself in danger as she is visited first by Garland's pitiful victims and then by the terrifying Rat Man himself.