Alone in the World
Fringe Season 4 Episode 3 (10/07/11)
Peter's attempt to reach are becoming more frenzied and hurting Walter terribly. He is now answering the calls he hears from Peter.
Olivia offers her help to Lincoln if he feels affected by being introduced to Fringe in any way.
Lincoln and Olivia's friendship is growing.
A boy infected with spores of some sort falls into Walter's care. The boy is inextricably linked to the source of the spores, making it more difficult to kill.
Using his connection to Peter, Walter is able to remove separate the organism from Aaron.
Walter starts to come to terms with his visions of Peter, and decides to give himself a lobotomy.
Olivia stops him and shares that she, too has been seeing a man in her dreams and produces a drawing of Peter.