Black Blotter
The radio previously collected by the Fringe team from the pocket universe (as seen in "Through the Looking Glass and What Walter Found There") starts to receive a strange signal, but when they look for Walter to decode it, they find that he has taken a dose of the hallucinatory drug "black blotter". When Peter asks him why he took LSD, Walter explains that he was desperate to remember the plan and implies that he thought this would help, but that he did not know they would be getting a message on the radio. He then confesses to Peter that he asked Nina Sharp to remove the pieces of brain that they had to restore to repair his brain after being in amber for so long; he asked for this because he felt he was becoming his old self who was a much crueler man.As Walter suffers from visions of his old lab assistant, Carla Warren and images relating to his first passage to the parallel universe (as seen in "Peter"), the rest of the team work with Anil to triangulate the signal from the radio. Peter and Olivia travel to the site in a nearby forest, and find the decades-old remains of Observers and members of the human resistance, including one with Sam Weiss's identification. The two recognize that Sam and his allies were defending a makeshift transmitter tower that was relaying the radio signal, and find where the signal is broadcasting from.
Walter is drawn by his hallucination of Carla to a spot in the lab where he had hidden a notebook containing many of his ideas, including the original design for the device to cross between universes. His vision of Carla claims that she died in a lab fire in trying to destroy the notebook. Nina Sharp appears in the hallucination and warns Walter not to read the notebook again.
Peter, Olivia, Walter, and Astrid travel to a boat dock across from the island site where the radio signal originates, briefly stalled by a Loyalist force. Upon the island, they find the signal coming from a house, where a couple, Richard and Carolyn, are staying along with the Observer child (as seen in "Inner Child") which Walter had hidden in the pocket universe with the help of an unknown person referred to as "Donald". They demand a password before they allow the group to approach that would have been encoded in the radio signal; Walter, through his drugged mind (we see a slightly surreal cutout animation in the style of Terry Gilliam of Monty Python fame), is able to assemble the password "black umbrella". The couple allow them in and prepare the child, whom they have named Michael, for traveling, and explain that they were former members of the Resistance forces; as they were ready to settle down, Donald left them with Michael for protection, and as per his instructions, they activated the radio signal every five days.
The Fringe team returns with Michael back to the lab. Olivia discovers that Michael still remembers her, despite having only met in the original timeline. Meanwhile, Walter, still in his drug-addled state, reminisces about his past and the damage that his more sinister side has done, and decides to burn the notebook. However, his hallucination of Carla warns that he has already done the damage, having recalled what he was capable of; when he next looks up, he finds he is looking at himself, a grim smile on his face. Walter snaps alert, finding no notebook and the lab empty.
