In 2004 a group of six students, who have newly arrived at university and quickly become friends, are beset by supernatural forces, which seem to centre around a 5th floor room in an otherwise innocuous student hall of residence. So insidious and terrifying is their ordeal that one of the six commits suicide, an act which drives an irreparable wedge between the rest.

Twenty years later, the remaining five friends are all living very different lives. Hannah Prentice is a divorcee with two children, the youngest of whom is being badly bullied at school, and a mother who is showing the first signs of dementia; Jess Maple is a professional artist, who is just about to break into the big time; Steve Lazenby is a successful architect, whose eight-year-old daughter is suffering from delusions and nightmares; Max Bradshaw is a self-employed plumber, happily married with three children, whose fourteen-year-old son has fallen in with the wrong crowd; and Michael Vance, bohemian and charismatic at university, is now a drug-addicted vagrant, who harbours a terrible secret…

Although the five friends have not been in contact for almost two decades, they are gradually drawn back together when their lives begin to fall apart. What happened to them twenty years ago seems to be seeping back into the present, affecting not just them this time, but their children, their partners, their loved ones. 

As the terrifying visions, the violence and the madness escalate, they must mobilise forces and once again confront the horror in Room 55.