Oliver Soames is a Detective Sergeant in the Metropolitan Police Service who is called out to an apparent open-and-shut murder-suicide which turns out to be the doorway into a world he never knew existed. All around us are Strangers - people with unique abilities to do things that most of us cannot. Soames finds himself inducted into the Metropolitan Special Circumstances Executive - a secret branch of the police force dedicated to monitoring the Strangers, and ensuring that they do not disrupt the lives of those around them. The only problem is that there appears to be a murderer on the loose - and it is one of them...