In 1937, a British-Belgian occultist arrived in Berlin to brief Heinrich Himmler on a secret society called the Green Dragon. Tracing his unbelievable claims, Chasing the Green Dragon dives into the interwar Parisian occult underground, where intelligence operators and esotericists mingled in the temple of the Polaires, Masonic lodges, and Maria de Naglowska's Luciferian salons, sometimes with fatal results.

A highly intellectual but eccentric scholar, Gaston de Mengel worked with René Guénon, the Cambodian Prince Iukanthor, and possibly with the French secret service - without realising it.

Based on a wealth of obscure sources, including new archival finds, the stranger-than-fiction story of Gaston de Mengel is a unique account of little-known cultural currents that gave birth to numerous post-war conspiracy theories and Nazi Mysteries - and Umberto Eco's Foucault's Pendulum.