High Quality Content by WIKIPEDIA articles! "Peter" is the 16th episode of the second season of the American science fiction drama television series Fringe, and the 36th episode overall. Considered a keystone episode of the series, "Peter" is a flashback episode, told as Walter Bishop reveals to Olivia Dunham that his son Peter is really the Peter of the parallel universe. Walter explains the events that occurred in 1985 that led to this, and the impact it had on the parallel universe to be at war with the prime one.