On February 27, 1933, the Reichstag (the parliament building) in Berlin, Germany, caught fire. A suspect, Marinus van der Lubbe, soon confessed, and portrayed himself as a lone-wolf arsonist. But Hitler had only just become Chancellor, and the fire gave him an opportunity to consolidate his power – he saw a broad Communist plot behind van der Lubbe, and soon prevailed upon President Paul von Hindenburg to suspend civil liberties to allow for the “ruthless confrontation” with that conspiracy. From the start, many anti-Nazis agreed with Hitler that van der Lubbe was merely a cog. On their account, the Hitler and his henchmen themselves had been the malefactors. Since the end of the Second World War, the hypotheses of the lone-wolf arsonist and of the Nazi conspiracy have vied for dominance. Defenders of the lone-wolf view need not harbor any Nazi or neo-Nazi sympathies: distinguished historians like Hans Mommsen, Ian Kershaw, and A.J.P. Taylor have take...