His, er, conversion to Catholicism came in 1885, when he began vociferously attacking free-masonry. His work Le Diable au xixe siècle (1895) was co-written by a Carl Hacks, although the name on the cover was 'Dr Bataille', supposedly being the confessions of a certain Diana Vaughan describing a satanic cult practised by free-masons. The book was a huge success with Catholics, and Thérèse was moved by the text enough to send a letter to Vaughan and write a play called Le Triomphe de l'humilité. In 1897 Taxil was forced to admit that Diana Vaughan was a mere typist and that the whole thing was a joke. Under police protection, Taxil left Paris.
Some photos of the church interior: