[WARNING: The following story contains spoilers from Sunday's episode ofBreaking Bad.Read at your own risk.]Cancer has always been a significant part ofBreaking Bad.It was only after Walt (Bryan Cranston) was diagnosed with inoperable lung cancer that he began cooking crystal ...

[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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Walt has been a malignant force on nearly every life he's touched since his 50th birthday. He pulled his partner Jesse (Aaron Paul) deeper into the meth trade, made him a murderer and took from him the love of his life. Walt's wife Skyler (Anna Gunn), who used to think smoking pot was a serious misdeed, is now Walt's partner in laundering drug money. Walt's actions got Hank shot and nearly paralyzed for life. And of course, there's the dozens of people who have died at Walt's hand.

On Sunday's episode, however, it became clear just how much everyone has been infected with Walt's darkness. Both Skyler and Saul (Bob Odenkirk) urge Walt to give Jesse the "Old Yeller treatment" after he almost burned down the Whites' house. Marie (Betsy Brandt) spends her therapy session fantasizing about the untraceable poisons she could use to kill Walt. And although Hank is now working with Jesse to catch Walt, he seems fine with Walt killing the poor boy as long as Hank catches it on tape.

"We wanted all these people crossing a line," co-executive producer Sam Catlin, who wrote and directed the episode, tells TVGuide.com. "We thought that the corruption of Walter White has sort of pushed Marie and Skyler and Hank and Jesse into places that are darker than they've ever been."

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Although Skyler has arguably crossed lines before, her pointed insistence that Walt do more than talk with Jesse is perhaps the most chilling. "I think that attacking her sister, threatening Hank and Marie, was probably the final straw for her," Catlin says, referencing the confession video Walt and Skyler filmed in the previous episode. "She's crossed over. She's in a place of intense self-hatred or self-annihilation almost. When you're in a place like that, you can have a very nihilistic point of view.

"She said in the past that she's not out to save herself anymore because she's as damned as Walt is," Catlin continues. "So, it's in for a penny, in for a pound. It's taken a long time to get her to this place, but she's put so much money in the middle of the table and lost it all. At this point, why not just bet everything?"

Surprisingly, the one person in this episode who doesn't have murder on his mind is Walt. He chastises Saul for even suggesting he kill Jesse and is further exasperated by Skyler's similar thinking. Is Jesse Walt's Achilles' heel? "Everyone is making good arguments to get rid of the kid. The irony of the episode is that everyone is sort of pitching murder and Walt is the one pumping the brakes," Catlin says. "I think Achilles' heel is exactly right. For reasons that [Walt] himself probably doesn't understand, Jesse is a soft spot for him and maybe one of the last little territories of innocence that he can protect. He's hard-pressed to let that go."

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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.

View original Breaking Bad Postmortem: Has Walt Corrupted Everyone? at TVGuide.com

Other Links From TVGuide.com Old YellerBryan CranstonAnna GunnBob OdenkirkDean NorrisBetsy BrandtJesse PlemonsSam CatlinBreaking Bad

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