I Am The Night
While reading Les Miserables this time through, I came up with this joke theory that Claquesous was a vampire. As introduced, he only ever appears at night, and no one ever sees him without a mask. I joked that it was to hide fangs.
Then after the gang is arrested, he disappears on the way to prison, mystifying the police escort. “He had simply vanished like a puff of smoke, handcuffed though he was.” Sure sounds like a vampire power to me! (Or maybe Batman.)
I kind of hoped Claquesous would remain a mystery, if only to keep the joke from contradicting canon, but in the end, Hugo provides an explanation: he was an undercover police agent. Even Javert isn’t aware of this, though he suspects it. (Need-to-know basis, I guess.) He dies at the barricade, having infiltrated the same group of rebels as Javert, but as a provocateur rather than a spy.