If a TV show isn't getting good ratings it goes "on the bubble." So how do the writers cope with the threat of cancellation hanging over their heads, and what happens when the bubble pops? We talk with two TV executive producers who know life on the bubble all too well. Liz Heldens is the creator of the NBC drama Mercy, which was recently cancelled after one season. Scott Rosenbaum is the show-runner of ABC's sci-fi series V, which after being on the bubble, has been renewed for a second season.