A matter of Time.
Gavroche gets sent back in time to Montfermeil, falls in love with the younger cosette there, and generally causes chaos. Did I mention time travel?
A NOTE ON MY USE OF ARGOT: While I will attempt to use argot where applicable, I have been unable to find any dictionary of French argot, and only a poorly sorted one of English argot. For this reason, until I find a better one, the only French argot used will be what I remember from the book, the rest being from the English argot dictionary I found and what little I know of cockney rhyming slang.
Gavroche walked by the abandoned cheese shop that had closed down a few years ago because the cashier had been shot by a man quite irritated that they had no cheese. It hadn't been particularly successful before then anyway, primarily due to the fact that it had no cheese. Gavroche had had no breakfast that day. He had had no breakfast the day before. 4 days before that, he'd been shot by national guardsmen and wounded to the extent that it made him stop singing and briefly pass out, although they'd healed up shortly after the barricade fell. This was becoming tiresome.
There was a legend among the gamins that the shopkeep had kept his most precious cheese in the back, unwilling to sell his horde to the masses. However, none of the gamins had investigated this rumor because loud bangs and flashes of light occasionally came from the shop, and they feared that it was either haunted or had a formidable automated defense system that no one had bothered to turn off. Gavroche was hungry enough to risk it. He wrenched a heavy board off the door and broke what was left of a windowpane with it.
He walked through the main chamber of the shop, climbed the cashier station, and pushed open the door to the back. He walked through it. It swung shut behind him and locked. This was part of it's defense system. Gavroche neither noticed nor cared. He felt his way along the walls of the corridor, looking for cheese, eventually finding another door. He opened it. It was filled with blue light. Gavroche looked behind him to make sure that he hadn't missed any cheese, and continued on to the next room. The source of the blue light was a sleek looking white machine, being tended to by a man with his back turned, frazzled hair, and a white lab coat. It was giving off some purplish light as well, but the majority of it was blue. Gavroche pondered this for some time, but hunger won out and he began scanning the room for cheese, still retaining some small hope that the legends were true, and that a vast cheese reserve had been left behind. Eventually, he knocked over a bucket to see if there was any cheese under it, which attracted the attention of the man, whom the reader has doubtless surmised to be a mad scientist. He turned to face Gavroche, a crazed look on his grease stained face, his eyes open wider than one would think practical. "So!" He cried excitedly "We meet again Mr. Bond!" Gavroche was clearly confused. His name was Gavroche Thenardier, not Bond. And even if his name had been Bond, how would this stranger know it? This briefly lead Gavroche on a train of thought wondering whether this man was able to psychically discern a person's name before remembering that he hadn't gotten his name right "Look me china plate, I've got no fight with you. I just want some cassan (cheese) and I'll go." The scientist either didn't understand him or didn't hear him, and fired back No Mr. Bond. I expect you to die." With this, he flipped on his machine, which engulfed Gavroche in purple light until he vanished. The madman took some cheese out of a nearby crate and ate it.