"Subject 9" is the fourth episode of the fourth season of the Fox science fiction drama television series Fringe, and the series' 69th episode overall. It was co-written by J. H. Wyman, Akiva Goldsman, and Jeff Pinkner. Joe Chappelle directed the hour. Plot Olivia (Anna Torv) experiences a strange disturbance in her home that creates a brief time distortion and attracts metallic objects to it before it dissipates. After explaining this to Walter (John Noble) and Astrid (Jasika Nicole), she and Astrid return to her home to examine the area, where the disturbance occurs again. Walter, observing this from his lab, surmises the effects are similar to one of his Cortexiphan children test subjects who displayed the ability for astral projection. Walter suspects the children who underwent the Cortexiphan nootropic drug trials are psychically linked, which is why Olivia is experiencing them. Walter can only recall the child subject as "Subject 9", but Olivia is able to secure records from Massive Dynamic naming Cameron James (Chadwick Boseman). While there, it is revealed to the viewer that, in this alternate timeline, the Cortexiphan trials were stopped after Olivia ran away from experiments as a child (à la Subject 13 but without Peter (Joshua Jackson) to bring her back). It is also revealed that Olivia now shares a much closer relationship with Nina Sharp (Blair Brown), who knew her growing up. Walter insists on leaving the lab for the first time in three years, joining Olivia to visit Cameron. Walter accidentally catches a glimpse of a letter from St. Claire's mental hospital in Olivia's coat; the letter is a request for Olivia's recommendation as to whether Walter should be reinstitutionalized or not. Arriving at Cameron's apartment, they find he has changed names and will not be back until the next day. Olivia sets Walter up in a hotel room to spend the night, but he suffers from a panic attack fearing the germs and contaminants in the room. He also reveals that his wife, Elizabeth Bishop (Orla Brady), killed herself much earlier in this timeline, just after Peter died. He tells Olivia that he is glad Elizabeth can't see him like this. Olivia offers to treat Walter to a root beer float, during which Walter reveals his discovery of the letter and that he came on this journey in order to demonstrate to Olivia that he is still useful. As they talk,