Originally Posted by Wazu
One other longshot weird idea is Tyrus, the henchman guy acting on his own. He seems to take everything very personally and actively hate Walt, and dislike Jesse. His reaction at the hospital was over-the-top when Jesse refused to come to work.
Yeah, Tyrus is my dark-horse candidate.
In any case, I still think the timing is an issue. If it was the ricin, according to what's been set up previously in the show it seems like the kid would have to have been poisoned before everything went down in the desert in order to present symptoms when he did.