This week's episode was a trip down memory lane for those that have watched the series since the beginning. Heck, we even got a look at Isaac Mendez again!
In a nutshell, here's what went down...
Viewers got to know Lauren, HRG's partner three years ago. She came close to having an affair with HRG, but he turned her down at the last moment. Still, there were clearly feelings there and it will be interesting to see what happens if/when she resurfaces because she got her memory erased by the Haitian after she got rejected.
Hiro tried to save Charlie. He appeared to have succeeded, too, by using Sylar to get Charlie's tumor out of her head. In exchange, Hiro revealed to Sylar his future.
By the end of the episode, just as Hiro was celebrating a life with Charlie, he stepped outside the diner and she was gone. Samuel was there. He said he had taken Charlie and forced Hiro to transport them back to present day. Once there, Samuel said the carnival's time traveler had locked Charlie in some unknown time (and then the time traveler subsequently died) and the only way Hiro would learn where she was would be to do whatever Samuel wanted.
And what was that? Samuel said he needed to go back and erase his transgressions. They started eight weeks ago. The camera takes us to that time and we see Samuel in a room, apologizing to a suffering (possibly dead?) man on the ground. It's Mohinder!