Dean Norris

Like most of the characters on Breaking Bad, Dean Norris' Hank Schrader is a long way from where he started at the beginning of the series.

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Once a blowhard DEA agent who provided comic relief, Hank's bulldoglike search for the meth maker known as Heisenberg has taken the character through a dark battle with post-traumatic stress disorder and, most recently, left him bedridden after being shot by two assassins sent by the Mexican drug cartel.

"He turned into a completely different guy at the end of Season 3," Norris tells TVGuide.com. "It's a show that does not take characters back to where they were at the beginning of the episode, and certainly not at the beginning of the season."

So far this season, Hank has been seen obsessing over rocks — excuse me, "minerals" — while making little progress with his physical therapy. Needless to say, Hank is in a pretty depressing place. "The whole concept for Hank was having everything that he was all about taken away from him," Norris says.

"His whole thing was physicality; it was being a big personality. His entire identity was wrapped up in being a tough guy... and it's embarrassing to have to have your wife change your bed pan."

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Indeed, Hank's wife Marie (Betsy Brandt) has been on the constant receiving end of Hank's vicious temper, which in Sunday's episode (10/9c, AMC) brings out some of Marie's old bad habits. Perhaps that's why Norris says Hank begins to become aware of his tone.

"In real life, you would be bitter and you might treat your wife badly. But you'll see soon enough that he feels bad about it," Norris says. "But he just can't help it. He's not unaware that he's being a d---, but he's also in a place where he's like, 'F--- you, I've just been shot. Somebody else has to take some pain too.'"

But Hank won't be in bed all season. Sunday's episode provides Hank with some fresh intel that will inspire him to speed along his recovery and renew his chase of Heisenberg. "Ultimately, you can't keep him down," Norris says. "We all need to have a purpose in life, and he realizes that at some point. And now, he's got a personal stake in it. Some guy shot him, and he wants to find out who it is ,.. He gets back into the juice, and that's what saves him ultimately. It saves him mentally, and it saves his marriage."

The irony, of course, is that Heisenberg is none other than Hank's brother-in-law Walt (Bryan Cranston), who actually spends time later this season carting Hank around as he steps up his investigation. "It makes for some tense, but funny, scenes, because I'm using him much more than I ever did before," Norris says. "[But Walt] also uses me. He can't tell how much I really know."

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Norris insists that he has no idea when (or if) Hank will ever catch on that Walt is the meth maker he's been chasing all this time. But he also suggests that Hank might have trouble bringing Walt down.  "Walt has always in the past, and also in this season, despite himself, looked after Hank in a way," Norris says. "He may help him get out of the whole thing."

But that's not to say that Hank's continued metamorphosis would ever mirror that of Walt's moral devolution, Norris  says. "[Hank] continues to be the guy that ends up morally in the right," he says. "He continues to be the guy who, through his determination and grit, ends up doing the right thing at the end of the day."

Breaking Bad airs Sundays at 10/9c on AMC.