If you haven't watched the end of last season, season three of Fringe, and want to, don't read any farther. But if you have seen it I have a few questions.
When Peter vanishes at the end and the observers comment that Peter was not important, he didn't matter anymore and that was why he disappeared.
Excuse me though, isn't Peter the one person that is important as far as the two worlds are concerned? If Walter hadn't kidnapped him in the first place, none of the destruction would have started on the other world. If Peter wasn't there to go into the machine how did the two worlds come together at the end?
I'm hoping, and reasonably sure, that they have explanations for these questions, but it makes me wonder.