I haven't seen the episode -- I've fallen horribly behind on Bones -- so I don't know if they sold the execution or not, but I have a massive problem with the concept, and it's this: Zach is very obviously autistic. He also is, as far as I know, the only opening-credits regular on any TV show who is autistic. They haven't actually come out and said it, but it seems fairly obvious that he is, and pretty much everyone I know who has an autistic child has said that he is, and they have praised the writers of Bones for handling it so well, as have I, especially since autistic people on TV are usually figures to be pitied or used in cop shows as murderers who don't know any better (like on a crossover between Law & Order spinoffs Special Victims Unit and Trial by Jury).
So to have Zach suddenly be a murderer, and have it apparently (and someone correct me if I'm wrong) be because he's so susceptible to suggestion by smarter people -- well, it's back to the stereotype. Instead of an autistic character who's succeeded, who's become a PhD and an important part of the team, he's just another victim of his condition.
I can't be thrilled with that, I can't be happy with that, and I can't be impressed by that. I'm willing to watch the episode before I actually condemn the show and/or the episode, but I'm not at all pleased with the overall choice.