Montag shows up at Faber's house after suffering a mini nervous breakdown after he realizes that he is completely unhappy and lives in a pretty messed-up society. Faber helps him to understand exactly what he has been missing out on, and envigorated with the knowledge, Montag suggests that they try to fight back somehow. He suggests that they start reprinting books again. Faber says that woudn't work, because the fireman structure would never allow it; they would get caught and burnt themselves. He says he would consider it if they could somehow get rid of the fireman system; a way to do that would be to
"arrange to have books hidden in firemen's houses all over the country, so that the seeds of suspicion would be sown among these arsonists."
Montag picks up on that immediately; he knows the firemen, and Faber knows old professors who could print books. So, that is the plan that they start with--to plant books in firemen's houses, and call them in to be burnt. They don't know the details, and are pretty scared about it all, but it is a start. For the first time in years, they feel happy and motivated.
I hope that helps; good luck!