The Heretics’ Revenge by Martin Barrett

Persecuted to extinction, the Cathar heretics desperately want revenge against the Church of Rome. It arrives in abundance 750 years later.

Condemned as heretics by the Catholic Church, the 13th-century Cathars are persecuted, tortured, and finally burned alive at Montségur. But according to legend they hide their riches and relic beyond the castle walls on the eve of their demise.
In the 1930s, Otto Rahn dedicates his life to recovering the long forgotten relic, and coerced by Himmler joins the SS to find the ‘Holy Grail’ for the Nazis. Exposed as both Jewish and homosexual, Rahn commits suicide. But not before he entrusts his notes to his niece. Notes that have never been found.
Seeking a challenge after retiring early, businessman Steve Jackson embarks on a modern-day search for the fabled Cathar cache. With French girlfriend, Manon Lubin, they locate Rahn’s abandoned clues in the Black Forest. The notes become a key to locating a religious discovery even greater than the Dead Sea Scrolls, and unleash a 750-year old time-capsule of revenge that threatens to shake the Church of Rome to its foundations.
The massacre of the Cathars and the true story of Otto Rahn are interweaved and then continued with the fictional search for the treasure and relic. Rich in historical detail, this fascinating and absorbing story, set in France and London, climaxes with a thought-provoking and controversial conclusion.