Fiorello. What is the mystery behind this word, and what is its sinister connection that binds a terrorist hiding in the Middle East, a serial killer in London, and a deranged woman and her American companion on the run in Europe? Fiorello. The genesis of this word began in 1978, when a secret experiment within the confines of the Vatican walls set forth a chain of events that would either validate the tenets of Christian faith . . . or destroy it.