This week, Heather and Justine take JB on a dark journey through the underground. First, Justine digs deep into the world of people who live underground in New York City. Full disclosure: the sickest thing down there is really just the rotting corpses of dead rats. But it's sick-in-an-interesting-way, so JB allows it. Next, Heather takes us down a very different sort of tunnel, where all sorts of unflushables lurk to ruin the lives of public works employees.