I have a theory on Dexter, let me know what you all think.

Harry believes he saw certain characteristics in Dexter that would eventually lead to him becoming a serial killer. So he 'trained' him to keep them in check and gave him a code. What if Harry's code is what made Dexter a serial killer? We already know that Harry had a bit of a conflict of interest when it comes to Dexter (he was banging Dexter's mom), what if by not getting Dexter the help he needed to turn Dex away from some of his sociopathic tendencies he turned him into a killer. The kid was traumatized by seeing his mother get chainsawed, of course he was a little weird. And how about the fact Harry completely abandoned Dexter's brother? Harry isn't the nice guy Dexter and Deb remember him as and I think he wanted to craft a weapon to get at the people he can't put away.