The Boy Must Live
Walter is recovering from the visions that the child Observer Michael gave him by touch, including that which revealed that "Donald," the man that helped Walter in the past with the plan to defeat the Observers, is really September. Realizing that the visions involved his sub conscious, Walter decides to use the sensory deprivation tank to explore the visions further. With Peter's help, Walter is able to review the vision of September as Donald, and locates the experience as having occurred in an apartment in Brooklyn. The Fringe team travels there with Michael, during which Walter reveals to Peter that he remembers things from the original timeline, including the relationship he and Peter had before Peter entered the Machine. Walter helps identify the correct apartment, and they find it occupied by September, who has not seen Walter for over 20 years.September explains that after helping the Fringe team in the past, the Observers had stripped him of his implant and performed a "biological reversion" to make him human. He and Walter had spent time together following this, and he chose the name Donald from Donald O'Connor from Singin' in the Rain. September further explains that in 2167, an experiment in developing human genes and sacrificing human emotion for intelligence, would eventually give rise to the emotionless Observers. The Observers developed asexual procreation techniques; in the case of Michael, he was created from September's genetic material, but came out as an abnormality, having both emotions and great intelligence. Michael normally would have been destroyed, but September decided to hide him in the past. September now suggests that by sending Michael forward in time to 2167, September hopes they would be able to prevent the experiment from being performed, wiping out the Observers from existence. Should this happen, time would possibly be reset from the point of the Observer's first interference with the past; Olivia takes this as a chance for them to see Etta again. Walter identifies the hologram of the plans given him Etta (as seen in "Letters of Transit") as those of the device that would be able to send Michael forward in time, which must be constructed from all of the components collected by following the tapes. The group, including September, leave to recover an item in a nearby storage locker that is yet another component of the device.
Elsewhere, Captain Windmark travels to his future of 2609 where he meets with other Observers, warning them that the child Observer has been located in their relative past. He learns of the child's relationship with September, and of September's past actions in helping the Fringe team. Windmark describes to his superior the interference of the Fringe team and requests permission to go back to a point in time where he could prevent it, but is refused, and told that his current operations are on their planned path. On his return, he learns of September's location, and with other agents, travels there, finding the apartment empty; a bomb rigged by September goes off, but Windmark and his agents escape in time. Loyalist agents help to identify the Fringe team leaving and roadblocks are put in place.
At the storage facility, September finds the device and gives it to Walter. Walter confides in September that he worries Michael's visions imply Walter may die from the plan, and realizes that September's warning, "the boy must live", from 1985 (as seen in "Peter") was referring to Michael and not Peter. September reminds Walter of the time he had received a drawn white tulip as a sign of redemption (as seen in "White Tulip"), and that he had recovered that letter for the future, as part of a notebook he had collected on the Fringe team. However, while he still has the envelope, the location of the letter itself is unknown, but September says Walter will find his redemption when he finds the letter. The team prepares to leave but Donald opts to stay behind. When they discover the roadblocks, they split up and make their way to the monorail station, which is heavily patrolled by Loyalist guards. Just as the train is about to leave, Michael steps off before Olivia can stop him, and he is taken away by guards to Windmark.
