September asks December to bring an initiating reactor to complete the time machine. Then he meets Walter, Peter, Olivia and Astrid and explains how the device works. Peter finds a farewell video tape from Walter addressed to him. Olivia and Astrid go to December's apartment to bring the initiating reactor but they find him hanged and the part taken by Loyalists and The Observers. Astrid suggests to use an Observer shipping lane instead. Olivia and Peter go to the Observer's headquarters and use chemical gas to retrieve a control cube to use the shipping lane. They also rescue Broyles that was interrogated by Windmark. Now they start to set in motion the plan to defeat The Observers.
Claudio Carvalho, Rio de Janeiro, Brazil
Did You Know?
The coded glyphs at the commercial break spell CLOSE. See more
The point of going to the future is to stop the forced evolution of the Observers. Walter and Michael make it to the future and the show ends with the Observers' invasion never happening because the Observers never happened, or at least not in the emotionless form we saw in the show. If that is the case, then September should not have been present at the Lake to save Peter and Walter; both of them should be dead. Also, if September never existed, then Michael never existed, so the invasion would still take place. What we should have at the end is Olivia, without Walter, joining Fringe Division and researching the Plan (an idea dropped early in Season 1). Of course, we could go back as long as the Observers have been observed in history (the historical prints and paintings shown throughout the series), so it is possible that none of this would ever have happened and we could be looking at a completely different time line.
However, if the observers did not ever exist then Walter would not have crossed over to the alternate universe and brought back the other Peter and they would not have been on the lake together and therefor would not need to be saved. The only reason Walter crossed over was because Walternate missed the cure for his Peter because September distracted him.
That actually does not mean the ending could not have happened. It was already established that the Peter at the end of the show did not belong to the current time line of this universe but was present anyway, so simply eliminating the observers would not necessarily also eliminate this preexisting paradox. See more
Dr. Walter Bishop
Peter, hold on to these tight. Anti-gravity osmium bullets. Shoot Observers with these and watch them float away like balloons.
If we shoot 'em, they're dead. Why'd we want 'em to float away?
Dr. Walter Bishop
...Because it's cool.
That makes sense Walter.
Performed by Tiny Music Box See more