I've been watching Dexter, up to episode 4. What is so subtle about John Lithgow?

Serial killers tend to be heavy and potentially overbearing characters, they may have a normal side but they also have an obviously menacing tick or give about them. Lithgow plays it in a way that doesn't make me think "that guy's obviously the killer, I don't know why everyone else doesn't see it immediately." It makes me believe that he is capable of being completely off the radar for 30 some odd years and get away with everything he does without raising suspicion about his actions. I think that's something fairly difficult to convey, and I'm not sure many other actors could have delivered this same essence. Hell, Michael C Hall doesn't always convince me and I think he plays the part very well.

At least that's my take on it.

Thank you for clearing that up, i just didn't get what you meant.