Act I ends when Bartleby announces for the first time that he "prefers not to" participate in basic office tasks – the Narrator is committed to finding out what is up with this guy.
In desperation, the Narrator picks up and moves his whole practice to another building, minus one very odd scrivener.
The final act contains the fallout of the Narrator's decision to abandon Bartleby at the old office – he's carted off to prison and eventually dies.