re: Someone explain the BB ending.

Well Walt knew Lilly of the valley was common, kids may get into it. He wasn't going to use ricin because he probably didn't want to kill the kid. He knew the cha ces of air oval were better with Lilly of the valley. But...if he died then that would be summed up as collateral damage.

He played on someone Jesse was close to, someone who was ok with killing kids to get a job done. Walt knew he had a day or two at the most to kill Gus. And he did..

With the poison he used the kid recovered an d it all looked like he just got into some local plant berries. Common for kids to do apparently.

So Walt's arse was covered, then he brings the fake ricin cigarette over and gives Jesse peace at mind. Was all good, perfect manipulation until Saul screwed up + spilled the beans.