In the height of summer 2013, Vince Gilligan, the creator of “prestige TV” phenomenon Breaking Bad, and fellow screenwriter Peter Gould, took a long walk around their offices in Burbank, California. The end was nigh for Breaking Bad, and they had just recently signed a deal to make Better Call Saul, a spin-off prequel series set around Bob Odenkirk’s popular shyster Saul Goodman, a criminal...