>> he said ah spezi, i forgot something. >> i never joke. >> and i never kid around. >> what did you take that to mean? >> well, it was a threat. in italian it's even more of a threat than it is in english. >> as you left his home after speaking to him, what did you think? >> well, me and doug, we were silent. we entered our car, and then almost at the same time, we say, it's him. >> if it was him, if carlo was the monster, it was a stunning moment. and it would make a great ending to their book on the monster case. but another author was also at work on that other theory of the crimes. >> translator: i believe i have done my duty, seriously and for many years. i wanted to make the recent developments official in my book. so that this story is not forgotten. >> florence police inspector michele giuttari was writing his own book, and who could blame him? books on the monster case are big sellers in italy.