Peter's actions of using the Wave Form Device to create a bridge between the two universes have caused him to erase himself from the timeline; a new timeline, in which young Peter was not saved by September after falling through the ice of Reiden Lake in 1985 after Walter's crossing, is set in motion. Despite the absence of Peter, the bridge has created a healing effect on the parallel universe, and both Fringe teams resolve their former differences and work together on cases.
