John Morrison

Character: Himself - Presenter / Narrator

Peter Jay

Character: Himself - DCI, Metropolitan Police, 1983

Iain MacDhùghaill

Character: Himself - Criminal Defence Lawyer

Archie MacLullich

Character: Himself - Consultant Psychologist

Pàdraig MacAmhlaigh

Character: Himself - Journalist

Julian Booth

Character: Himself - Forensic Psychologist

Brian Masters

Character: Himself - Author, 'Killing for Company - The Case of Dennis Nilsen'

Elizabeth Scott

Character: Herself - Nilsen's Mother

Neil McKinven

Character: Dennis Nilsen

Ryan Fletcher

Character: Victim Jamie

John Paul Hurley

Character: DCS Chambers

Lewis Brown

Character: Young Nilsen

Finlay McLean

Character: Nilsen's Grandfather

Nicholas Underwood

Character: DCI Peter Jay

Andy Marjoribanks

Character: Solicitor