“Alone in the World” is episode three of season four of Fringe.
Dr Sumner is talking to Walter, checking that he’s taking his medication and how he’s doing, one of the monthly evaluations that were a condition of his release. He also asks about Walter covering up reflective surfaces and claiming there’s a strange man in the lab, and Walter eventually admits he’s been having hallucinations, caused by his own alterations to his meds. But the last one was weeks ago. Which isn’t true; he’s seeing Peter in the back of Sumner’s clipboard.
A boy is running from two others. He ducks into a tunnel and they follow. One is going to beat on him when the other says something has touched him. Then both start getting wrapped in black veins of something. The first boy runs away.
Olivia is searching in a database for someone when Lincoln comes. She wanted to see him and checks if he’s okay and handling everything and not freaking out. He’s fine. Olivia tells him she’s there if he needs to talk. Then gets a call from Broyles.
At the tunnel, Broyles tells them they have the bodies of two 12 year old boys. Seeing how badly decomposed they are, Lincoln asks how many months they’ve been missing. 10-15 hours. Astrid comes out of the tunnel with Walter’s remote viewer and Broyles asks her what Walter has. Astrid interprets Walter’s ramblings as he has no theories. Inside the tunnel, Lincoln finds a third set of footprints.
Broyles and Astrid accompany one body back to the lab and Broyles checks on how Walter is doing. Dr Sumner said that Walter was unusually agitated and had something he was reluctant to share. Walter starts explaining he wants both bodies, then responds to Peter saying his name. He’s trying to talk but hearing Peter and blurts out that he isn’t losing his mind. Olivia calls Broyles; they have a lead on the third person. A kid at school was heard saying the two dead boys had plans to beat up a third. She and Lincoln find him at the school.
The boy, Aaron Sneddon, is brought to the lab and Olivia tells Broyles he’s no father, his mother is out of the country and Aaron has been left to stay with a neighbour as usual. Olivia then tells Aaron that they need to give him a check-up. Aaron doesn’t like doctors. Olivia says he will like Walter; there’s nothing scary about him. Then Walter comes in in a fluid-spattered apron definitely looking scary.
Walter takes a blood sample from Aaron, then shouts at him for touching one of Peter’s toys. Then apologises, saying it belonged to his son, and ends up explaining that Peter died as a boy. Astrid comes in and says Walter needs to look at something. She moves a candle near the body and it goes out. The body is pulling high levels of oxygen from the air. Walter notices that there’s more mould. Then shouts they need to get it into the incubation case quickly. They manage to do it before the body explodes with spores. Walter thought the mould was a symptom of the decomposition; it’s actually the cause. An aggressive form of fungi that killed the boys.
Astrid calls Lincoln and Olivia who are heading to the morgue to get the other body to warn them that they need to evacuate the room and get the body locked down because it’s going to explode with spores, then calls the morgue itself. No-one answers quickly enough and Lincoln and Olivia arrive just as it explodes. Olivia tells Lincoln they can’t open the door. The people inside are already dead. The morgue is covered with mould when they enter in hazmat suits. According to Walter, it’s a parasitic fungus that grows rapidly.
Walter strikes up a bit of a friendship with Aaron, and tells him how both sons died. With the Observers not intervening when Walter went to get the Peter from the other side, he died as well. This leads to Walter seeing Peter, figuratively not literally, in Aaron, which causes issues when the fungus proves to be more complicated than thought. And, by the end of the episode, Lincoln does feel a need to have that chat with Olivia.