SPOILERS APLENTY!

Walt poisoned Brock. Here’s why:

  • Walt snapped when Skyler, in giving the nest egg to Ted, took his only way out. The maniacal cackling was him finally breaking.
  • At that point, it was all laid bare: it’s Gus or Walt (and Walt’s family, including his infant daughter). Walt had to play all of his cards.
  • His only way to get to Gus was through Jesse.
  • The idea of poisoning Brock was planted, as Jesse intuitively observed, when Walt saw Brock happily playing video games on the couch at Jesse’s place.
  • It was decided upon when Walt spun the gun for a third time, and it stopped on a plant, a harmless fixture in the background.
  • Walt was off-screen almost the entirety of the last episode. We were led to believe he was holed up at home, but there is a narrative gap that can be filled.
  • Walt knew that Jesse would ultimately agree that Gus was the only one capable of having a child killed. After all, he had done it before.
  • And remember Jane. He’s done this to Jesse before, albeit indirectly. This is the next, chillingly logical step.
  • Gus therefore dies. The final 18 episodes are Walt in some form of ragged command of the industry, with the cartel out the way. The main conflict is Walt v. Jesse v. Hank.

This would be the ultimate, and internally consistent, turn towards super-villainy for Walt. The one Vince Gilligan has always spoken about i.e. how do you turn Mr. Chips into Scarface?

Prove me wrong, children! Prove me wrong!