For an avid aficionado of mysteries there must be something odd about a whodunit in which probability replaces the butler. Knowing the rules of the genre the reader expects that, no matter how inventive the plot line and the resolution, the standard features of the story will remain unaffected. The central of these inviolable rules is that the investigation must lead to the apprehension of the criminal. "Justice must be done," is the tacit moral imperative of the crime story, faithfully observed by its practitioners.

Even the so-called police procedural, by far the most realistic in their treatment of criminal investigations, do not let perpetrators go free at the end of the day.

Although the reality of police work is often different, even the most accomplished writers of police procedural, such as Ed McBain or Maj Sjowall and Per Wahloo (the authors of the brilliant Martin Beck series...