The long Baal Shem Tov story, part 1

The Baal Shem Tov sends his talmid Moshe Meshel to deliver two letters, both to residents of Lvov. The first, to the Av Beis Din R. Chaim Rappaport, contains mysterious instructions for an upcoming journey. The second, to R. Chaim Yisroel the Potter, is delivered in silence. Unbeknownst to anyone, Chaim Yisroel is a hidden tzaddik who must act soon to prevent a calamity.