Twice in the fitful life of the Third Republic, Paris was convulsed by a criminal scandal with a Jew at its heart that split public opinion and sent crackles of disquiet through Europe. The first of these, the Dreyfus Affair, has become shorthand for the anti-Semitism, xenophobia and venality that streaked the political culture of fin de siècle France. The second, the murder in 1938 of a minor German diplomat by a refugee from Nazi persecution, is now all but forgotten – or if not forgotten, then reduced to a tiny footnote in the grand tragedy of the genocide of Europe’s Jews. In this engaging history, which at times reads like a thriller, the American journalist Jonathan Kirsch sets out to illuminate this murky episode and rescue its protagonist from obscurity.

Early on 7 November 1938, a slim, stunted boy of 17 with sullen eyes and bitten nails exited the Hôtel du Suez on the boulevard de Strasbourg. He paused for a moment in a gun shop before continuing to the rue de Lille, where the solemn portico of the German