Thomas talks to Teresa about going back in time to save them
I don't think that's a very good idea Thomas....
Chuck realizes that it's Thomas and runs away with him
I'm going to do it, I'm going back to save them
Thomas sneaks out but has to be careful not to run into anyone.
What? Who said that?
While they are running back, Thomas slowly disappears. The reason Chuck had died before was because he had saved Thomas. Chuck ran away with the future Thomas so he wasn't able to save the past Thomas. Thomas had died and Chuck had lived.