Agent Hank Schrader (Dean Norris) is one scary dude, but only if you’re manufacturing, selling, transporting or using drugs. If you’re not doing any of those things, he’s a big, harmless doofus. If you are doing any of those things, he’s a doofus savant — a tireless, grim, insightful and even, at times, ingenious DEA supercop. Now that he’s mended after his utterly insane parking-lot shootout with the cartel assassins, Marco and Leonel Salamanca, and fully back in the hunt for Heisenberg, Hank is exactly the sort of trouble that Walt and Jesse do not need. That he’s Walt’s brother-in-law and frequently discusses his pursuit of the Southwest’s premier meth cooker with Walt — a.k.a. the Southwest’s premier meth cooker — only adds to the show’s bracing, paranoia-driven unease. Will Hank figure out, conclusively, that Walt is indeed Heisenberg? Perhaps more to the point: Will Walt and Jesse allow Hank to live long enough to do anything about it?
I think Hank is already fostering the idea that Walt it connected somewhere. I don't think the character is dumb enough to completely disregard all of Walt's strange behaviour, and if he has worked out that Walt is involved then I think he'll keep that to himself until he can fully connect all the dots. I'm awaiting the moment that Walt, or Skylar, or whoever, tells Hank that Walt's up to something to which he replies: ''I know''.