The black hat society

Another Venice secret society, mysteriously linked to the infamous Mister circle... I was hired to investigate a series of crossings into alternate realities. My only clue was that there was always the appearance  of a woman with a black hat and the existence of a strange 'bubble tunnel" through which everyone had to pass through. All I had to do was follow the Mister, that enigmatic figure that had introduced me to all kinds of secret groups and societies in mystical Venice. My report after this investigation: simply... inconclusive.