"I'd unleashed something and I wondered what more words might do, a sentence, several sentence, if I managed to lock the door and bar her at the exit while I held forth on some topic that might have concerned me, or even addressed the growing bond between us, since we had never once spoken about our relationship.
I had all the power of a child" 226
This passage is from when Sam is with Marta and he has the serum so he is able to speak. He says a word to her and she starts to feel sick so she gets up and leaves. I think this shift in power is really interesting because Sam has felt the pain that he is now trying to inflict, and yet he is still tempted to use it. I think that's something that mirrors what some people do in real life, which is sad.
For example, sometimes when people have been hurt or bullied, their reaction is to bully other people around them so that they can feel what it's like to be on the other side. Personally, when someone does something that I don't like, I try to make sure I don't do the same thing to other people. I'm not saying that I've never hurt anyone by mistake, but some people hurt others purposely. I feel like you'd have to be really broken to get to that point.
Also I thought it was strange that after seeing that Claire was alive he would still go back to Marta. He obviously still wanted to protect Claire and he did a lot to do so, but this just seemed like an unnecessary plot point. Authors often have their main character be somewhat moral, but with some flaws to make them more relatable, but I don't really find Sam relatable personally. I think I identified more with Claire, but that's just me.