Back in 2000, I moved to Italy with my family to write a murder mystery set in Florence. We rented a 14th century villa on a hill just outside the city, looking out over a lovely olive grove.

I soon discovered the grove had been the site of one of the most horrifying double-murders in modern Italian history, committed by a serial killer known as the Monster of Florence. The Monster killed young couples making love in the Tuscan hills, mutilating the female victims and taking away their sex organs. He was never caught.

In the olive grove outside our house, however, the Monster made a mistake. He killed a gay couple making love, in which one of the partners was young and slender with long blond hair. When he discovered his error he was furious, trashing the site and ripping up a gay magazine he...