Originally Posted by wiggo
The more interesting question about the rune is how they knew where September was going to step (or even that he would be there at all).
There are a couple of scenarios that can explain that.
For example, The Observers (or the evil faction of them) know September is rogue, so they intentionally send him to that point in time in order to trap him.
Remember, September gets captured after
this episode in his timeline but those events occurred several episodes ago for everyone else. September doesn't explain what happens in the future to Peter until he's been shot, so September already knows back then he has nothing to lose and he's been betrayed. In this episode though September still assumes he is safe.
The Observers could also be colluding with Bell and have been working with him all along; giving him the technology necessary to capture September and shoot him with a weapon designed for the task with their help. Possibly a weapon they can also use to fight the dissenters within their own group.
The problem with that is if Bell's great plan is to collapse the universes then won't it destroy The Observers too? If part of the plan is that the new universe would also have become a new place for them to live, then it would explain why they are pissed enough to go back in time to the present day and enslave humanity.