Valjean walks down the sewer carrying marius singing a jolly tune:

Here I come a carrying
Among the sewers so green
Here I come a-lurking so fair to be seen
My back is killing me
Why don't I JUST LET HIM DIE
He'll just float up to good ol heaven anyway
I'll go tell cosette that he's just on a break...

*valjean drops marius and runs away*