I've just finish reading (sorry for my bad :( I'm too late)
I think Nolan just wanna be a human like John but he don't understand how human is.
all the things that he wants is the love from John, but John just want Nolan for do his housework.
I think Nolan might be feel bad and lonely inside his mind, so he had to against John.
I think maybe Nolan doesn't want to do harm John, 'cause the deep inside Nolan is a good robot.
p.s. can you understand my meaning? I'm so sorry for my bad English -_-