The fourth in Sjowall and Wahloo's Martin Beck series is as complex and accomplished as its predecessor, The Man on the Balcony. It's the most successful of the series internationally, winning several awards and becoming the basis for a film starring Walter Matthau. This time Martin Beck and his colleagues are trying to solve the mass murder of nine people, gunned down on a bus late on a rainy Stockholm night. One of the victims is a young murder detective. What was he working on? Why was he armed while off duty? Was he, despite being married, somehow involved with the nurse sitting next to him or are the killings connected to the one passenger nobody seems able to identify?
With such a high profile case, detectives are drafted in from across Sweden to assist, allowing Sjowall and Wahloo to reflect on the harsh, chaotic nature of Stockholm compared to the more rural areas of the country. The welfare state is a theme too, with the Marxist authors observing the corrupting effect of failures in the system.
And there is time to examine the role of the police themselves. The bus massacre is juxtaposed with an anti-Vietnam demonstration at the American embassy. While every available policeman is pressed into service there, tormenting those armed with no more than placards, the real criminals can work unmolested.
Martin Beck's daughter, once proud of her father's profession, is now 16 and tries not to mention his work to her friends. People want to pretend the police aren't there, Sjowall and Wahloo explain, until they really need them.
It would be easy for the authors to overdo their point by throwing in one or two obviously corrupt cops but they don't. A couple are incompetent, a few are bullies but basically they're ordinary men (and they're all men, in almost every book) trying to hold together a crumbling society.
This is another deeply intelligent entry in the series.