AMC’s “Breaking Bad” is back, and that’s nothing but good news for fans of smart, cinematic, well-written drama, especially in a summer devoid of “Mad Men,” which won’t air new episodes until early next year. It’s probably true that “Breaking Bad” is a tougher sell than “Mad Men” because the stakes are so much higher. “Breaking Bad” is a challenging show that revels in making viewers squirm. Not all viewers appreciate that edge-of-their-seat nervousness. But those who do recognize there’s no sweeter discomfort than an hour of “Breaking Bad” (10 p.m. EDT Sunday).

When the show ended its third season last year, cancer-stricken (but now-in-remission) chemistry teacher-turned-meth maker Walter White (Bryan Cranston) ordered his flunkie, Jesse (Aaron Paul), to kill his former lab assistant, Gale (David Costabile), to keep their boss, Gus (Giancarlo Esposito), from killing them.