I touched on this briefly in the tags & pretty similar point as the last post but how awful to have this metaphor (from when javert is pursuing valjean & cosette into the alley by the convent):
occur to valjean here as an explanation when he's wondering why javert is behaving out of character:
because this is not at all why javert is behaving this way (the second time) -- he gives this strange line in a strange way because he's lying for the first time in his life, and he's going to let valjean go, and then he's going to go kill himself over the profound moral crisis he's having. he's incredibly serious & emotionally distraught & doing a good thing that goes against everything he's believed in his life up til now -- but you can see why valjean, particularly having experienced the former passage (albeit not from javert's pov), would come to this conclusion! look at his experiences with javert he has to go on! and now he's tired and sad and has resigned himself to being arrested and can't conjure up the energy to puzzle out whatever's going on with javert and this makes sense based on what he knows about him. and that's the last they see of each other! head in hands it's so.