On the DVD of The Hunger Games: Catching Fire there is a deleted scene which shows Plutarch Heavensbee exchange envelopes in some secured vault. He burns the one in the vault and replaces it with one from his pocket. Given that this envelope is in a box with the number 75 on it, it's likely that it's related to the "Quarter Quell".
While there is probably not much to it, being a deleted scene anyway, I'd still like to know what he was actually doing there. Is this elaborated further in the book or is this a movie-only extension? As we learn at the end, Heavensbee, though being Snow's new game maker, is actually part of the revolution. So I'm wondering was this action part of his official job for Snow, somehow changing the rules in order for the victors to fight in the 75th games? Or was this part of his inofficial role in the revolution, trying to somehow bend the game's rules for their plans?
(In the latter case it would be kind of a foreshadowing, even if the (book-unaware) audience would likely not have classified it as such and rather sticked with the former explanation, but after all it would raise some doubt. And was maybe even deleted because of this?)