On a steamy August night in 1952, a British family settles down to sleep beside their car in a lay-by. Before daybreak all three of them, a father, a mother, and their ten-year-old daughter, have been brutally murdered.

In a remote corner of Provence two worlds collide under a full moon. The British family are pioneering scientists and cosmopolitan; the French family accused of the crime are farmers defined by their land and codes of conduct which struck outsiders as feral. The accused farmers closed ranks and lied repeatedly in the shadow of the guillotine and to save the family's honour. An inspector calls. With extraordinary tenacity he tracks down the man dubbed 'the monster of the farm of the damned'.

This is the true story of the most contested murder in France since the Second World War, the inspiration for films and tales of espionage, hit squads, wartime bullion treasure, and chemical weapons research. Doubts still linger locally in this part of France as to the final judicial outcome. Conspiracy theories about the reason for the murders are routinely aired, and some family members of the man finally convicted of the crime still claim his innocence.