This is a very unusual episode of Fringe. Anxiety caused by Peter's disappearance leads Walter to smoke some funky marijuana. Walter then tells Olivia's niece a story, and his imagination becomes the setting for a musical mystery put on by the rest of the Division.
This week's episode is titled "The Man from the Other Side." In it, Newton and his shape-shifter goons are trying to open up a portal into our universe. Peter also learns that he is not from our world, with heartbreaking consequence.
This week's episode has a cool name. It's titled "Olivia. In the Lab. With a Revolver." The Division is puzzled by the death of a woman from a disease she apparently never had. Meanwhile, Olivia struggles to keep the secret about Peter to herself.