People go missing every day in the Scottish capital, where Luke Calvin treads the tightrope between the law and order of the police and the harsh realities on the streets. Existing in his own personal grey area and plying his trade as a private investigator in the shadows of Edinburgh, he operates at the behest of the "office" - nothing more than some semi-official voices on a phone and a steady paycheque for doing the work that they can't be seen...