We finally do get back to Jean Valjean and Cosette, and in a strange turn of events, the narrator names them on the first page!
The Rue Plumet house has a secret entrance on the other side of the block. I’m trying to remember how this comes back later, other than by keeping them hidden along with the decoy apartments, one of which Valjean abandoned after Marius found it, and one of which he’ll go to later on after the robbery attempt here.
Cosette has finally grown into her childhood nickname, with the “voice of a lark.” Back then, in Montfermeil, the name was ironic, because “poor Alouette never sang.”
It’s not often that Les Misérables backtracks over the same scene from a new point of view, but it’s a good thing it does when showing Cosette’s side of her long distance flirting with Marius. It shows us that it really is two sided and not all in Marius’ head.
Here’s an odd POV case: When Theodule (Marius’ cousin) catches Cosette’s eye, the narrator doesn’t stick with what Cosette knows, he jumps over to Theodule, names him, then jumps over to Marius to clarify the timeline, then back to Cosette.
Some quick googling on the history of PTSD suggests it has long been observed in soldiers and veterans, though often attributed to either physical injury or character failings. It doesn’t seem to have been understood more broadly until the late 20th century, certainly not in 1862. Even so, Valjean clearly experiences a PTSD flashback when he and Cosette see a chain gang leaving Paris for years of hard labor in prison.