Yeah, Ted Sprague, the "radioactive man" is clearly the key to the atomic explosion in NYC.

I see things unfolding like this...

The midseason climax point with be stopping Sylar from killing Claire. This will serve as the event that will fairly solidly unify the main characters (Peter, Nathan, Issac, Hiro, Claire, possibly even Niki, D.L., and Micah). From what I've read, I think this will be mostly wrapped up by the end of the first run of episodes (Dec. 4). At that point, NBC's going to air reruns through the Holidays.

The season ending events will drive toward preventing Ted from blowing up and taking NYC with him. I'm guessing there will be a cliffhanger at which we're left all summer wondering if the Heroes were able to prevent Ted from destroying NYC.

IOW, the "Heroes'" goals are...

1. Save the cheerleader (from Sylar)
2. Save the world (from Ted's super-nuking powers)

We all wear a green carnation.