With an introduction by Sean and Nicci French (another husband and wife crime-writing partnership), The Laughing Policeman is the fourth in the Martin Beck series by Maj Sjowall and Per Wahloo. In many ways it is the most socially critical and effective so far, dealing with corruption, cyncism and murky dealings in the world of business and the Stockholm underworld. The laugh referred to in the title is not a joyous laugh, but one of worldweariness, tragic irony and realisation of the imperfection of society, only made clear in the very last sentence of the book. Starting with the mass murder of several people during a shooting incident on a bus, including an off-duty detective, one of Beck’s colleagues, it soon becomes a story concerning sordid secrets from the past. This the most carefully and satisfyingly plotted novel of the series so far.