Originally by Mark Means.
You've heard that old saying, "that's the oldest trick in the book", right? Well, I have read that book.
You know how to spot cons, from the simplest tricks to the most complex confidence games. You also know "new angles on old tricks" and can fool even the most experienced grifter. You are basically immune to Deceit.
By spending a Fortune Point, the GM will tell you if you are being conned and how.