Anna Gunn, Bryan Cranston Anna Gunn, Bryan Cranston

[WARNING: The following story contains spoilers from Sunday's episode of Breaking Bad. Read at your own risk.]

Cancer has always been a significant part of Breaking Bad. It was only after Walt (Bryan Cranston) was diagnosed with inoperable lung cancer that he began cooking crystal meth to provide for his family. Five seasons later — after remission and following Walt's complete transformation into a murderous drug lord — Walt's hoping the return of his cancer will keep him out of the clutches of his DEA brother-in-law Hank (Dean Norris). But the cancer at the center of the show is no longer the tumor on Walt's lung — it's Walt himself.

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But that could be about to change. Thanks to Jesse's burning rage over Walt poisoning  Brock, Hank is finally able to convince Jesse to rat out his former partner. "Jesse finally realizes that he hates Walt more than he hates Hank," Catlin says. "He's finally ready to do whatever it takes to get this guy."

Or is he? After Jesse spills his guts to Hank, they both realize there is no physical evidence to corroborate Jesse's story. And when Hank sends Jesse to have a sit-down with Walt while wearing a wire, Jesse gets spooked. Instead, Jesse runs to a nearby payphone and tells Walt he's coming for him "where he really lives." Although Jesse tells an angry Hank he has a better plan, Jesse may not live to see it through. After Jesse's threat, Walt calls Todd (Jesse Plemons) and ominously suggests he "may have another job" for Todd's uncle, who helped Walt kill 10 witnesses in prison.

"We'll have to see exactly what [Walt] means by that," Catlin teases. "But I'll say this:  Walt has bent over backwards time and time again. He's put his business and he's put his family, his real family, in jeopardy to stick his neck out for Jesse. In this episode, he comes to that plaza in good faith and Jesse, once again, lets him down. So, his options are narrowing in terms of what to do about Jesse."

And it's safe to assume that everybody might be crossing more lines in the final four episodes. "I think you should be concerned for all the characters and what they might do," Catlin says.

Breaking Bad airs Sundays at 9/8c on AMC.