I've been struggling with the issue of titles for my works in progress. For Book One, I originally used a great title which all my beta-readers liked, but it no longer fits the book, so I really have to change it. And I wanted at least a working title for the sequel, rather than "Secret Theatre Book Two" :)
Thus, Book One is now "The Guiser". A guiser is someone who goes in disguise, specifically (in regional British dialects) a mummer in one of the winter celebrations. The title works on several levels: at least two characters disguise themselves at some point (one of them for the whole book), and many of the others are not what they seem.
The title of Book Two, "Treasons, Stratagems and Spoils" is taken from "The Merchant of Venice". I'm not sure yet how well it will fit, but when I heard the phrase during Saturday's performance it immediately clicked.