Thief: Ezio, one of the Cento Occhi (Hundred Eyes) leaders has worked his way into our own guild! He is an accomplished liar, responsible for the deaths of many of our brothers. Come, I will lead you to him.
After leading Ezio to a secluded location, the thief signalled the Borgiaguards, and revealed himself to be the traitor. Ezio defeated the opposition and assassinated him.