A fantastic start to the fourth season of the best show on television!
I need to re watch episode 3.22 "The Day we Died" I could swear the Observer August says to Observer September that Peter Bishop never existed.
Season 4 episode 1 "Neither here Nor There" begins a week after Peter Bishop unites the two warring universes and seemingly vanishes from existence, Lincoln Lee and his partner chase a man into a warehouse Lee's partner is killed by a mysterious translucent man. Olivia informs agent Lee that she will be taking over the investigation, Lee refuses but Olivia pulls rank...a rank Lee is totally unaware of and drives off. Not satisfied Lee tracks Dunham to the Lab at Harvard where he meets the Fringe team. Just as Olivia is about to rip agent Lee a new one she gets a call of another incident this time involving a female driver.
Meanwhile Observer September is tasked with ensuring all of Peter Bishop's existence is totally erased. He visits an antique shop to collect the parts he needs to build a device that will erase Peter Bishop forever. Once completed he sits outside the Harvard lab with the device concealed in a briefcase, September pauses then shuts the briefcase and walks off in the night.
Dunham and Lee eventually track down the translucent mans hideout Dunham kills one but Lee realizes there's a second and tracks it down and kills it. Afterwards Olivia decides to bring Agent Lee up to speed and takes him to the hangar where the machine is.
"Neither Here Nor There" was a great episode that effectively shows effects of Peters decision in the final episode in season 3. There are new threats to our universe, but are they from Walternate or a newly created threat resulting from Peter Bishops decision? Also Peter has not been completely erased from existence because he is seen by us the viewers for a fraction of a second and apparently Walter has seen him but doesn't recognize him...or doesn't recognize peter as an adult. Walter does mutter something about seeing the one you love die twice. Is one of the effects of Peters decision that in this timeline both Peters die? I think the effect of Peters choice is that he now exists in a third universe.