Todd begins to delicately turn Walt down, but Lydia never met an advantageous business deal she didn't like. She asks how much. "Nothing short of a million," Walt says. Todd isn't sure if Jack would go for this, and I wonder how much Todd's begging off is because he doesn't want Walt to see what he's done with Jesse. Walt is aggressive, though; he offers to come to the compound tonight. Just to talk to Jack, to try to convince him this is a win-win situation. The waiter arrives with Lydia's tea, which is her cue to shove Walt along. Todd expresses his doubts to Lydia privately and she's like, "Hey dummy, of course we're not doing business with him. Don't make me have to walk you through it." In other words, they're not going to do business with him; they're going to get rid of him. "Did you look at him?" she asks. "You'd be doing him a favor." At this, Lydia tears open her Stevia packet and considering the way the camera fetishistically lingers on the granules as they tumble into her mug, obviously this is how Walt has decided to deploy his ricin.
So about this ricin in the Stevia. Two questions: how and why? The "how" has fewer options, but none of them very plausible. Walt was able to steal a packet, open it imperceptibly and seal it back up again also imperceptibly. Walt was able to print out a fake Stevia paper and seal ricin within it to make it look like a real Stevia packet. Walt used some of his money to but a Stevia plant and had this packet professionally made. The bottom line is I think Lydia is too paranoid not to have noticed a tampered packet. As for the "why," the most correct answer is "because the fans wanted to see it." They wanted the ricin used, they wanted Walt to tie up loose ends and they probably wanted the haughty bitch with the twitchy attitude to die. From a character perspective, I suppose it makes sense that Walt would have wanted to bump off the woman profiting off of his blue meth in his absence. Certainly more sense than the theory I've seen advanced where Walt wants to cut off meth production in New Mexico. That kind of altruism is not on Walt's radar. Mostly, though, I don't think Walt has a very good reason to kill Lydia. Honestly, if you told me he didn't want to ricin -- ricin that he so ingeniously created and then hid for a rainy day -- to go to waste, I'd say that's as good a motivation as any.
After the break, we're out in the desert, for a Walt Builds Something montage. He's got jumper cables and a car battery and a drill gun and an electric saw, and of course his automatic rifle. Clearly, he's creating some kind of apparatus with the gun. Something that helps him gain an advantage over a room full of Nazi thugs with only one weapon. He hits a button on his car keys, and that triggers a mechanized arm to spin round and round. I'm not going to pretend like I don't know how this ends up, but it's also not all that difficult to put the puzzle pieces together here. While he works, his little hemp necklace with his wedding ring attached tumbles out of his shirt. Somehow Skyler is still on his mind.