(Back to the third-person narrator and his righteous indignation.)
Woodcourt is back trying to doctor the miserable poor people in Tom-all-Alone's. This is why he doesn't have any money, remember?
Walking around, he sees a woman on a stoop with a huge wound on her face. Of course it turns out to be... Jenny! Dickens's world is full of crazy coincidences.
Woodcourt is super nice to her – he has an ability to talk to the poor as if they were actual people. Oh yeah, crazy.
She's nursing yet another beating from her husband but seems OK.
When he's done with her, Woodcourt sees a boy creeping around the corner. Jenny runs after him, yelling, "Stop him!" – and Woodcourt does, thinking maybe he just robbed her.
But no. This boy is none other than... Jo.
OK, the surprises are not even all that surprising anymore.
Woodcourt recognizes him from the inquest, but Jenny knows Jo ran away from Bleak House after being taken in by Esther when he was sick.
Woodcourt hears this and is half nauseous, half ready to cry. Jo is patient zero of that horrible disease that disfigured Esther's face.
Jo is horrified and sorry that he infected Esther.
Still angry, Woodcourt asks Jo why he left that night.
Turns out Jo didn't run away at all – he was taken away by... well, we don't know yet, since he just whispers the name to Woodcourt.
The guy took him to a hospital and gave him some money to stay far away after he was released (which, considering he is still really sick, shows what hospitals were like back then – pretty much just places for poor people to go to die).
He stayed away as long as he could, but now he's run out of money, so he's back at Tom-all-Alone's to die.