The main esoteric schools of religious and mystical theory and practice in Europe between the turn of the era and the Middle Ages are gnosticism, merkabah and catharism. Stoyanov shows how these and other threads of European mysticism are in fact a single stream. The unifying factor is the Bogomils. This underrated and understudied sect - the name means grace of God - was introduced into Bulgaria by 3 shadowy figures, flourished there for 4 centuries, and then spread throughout Europe.