When two teenagers on a date turn up "dead" at an abandoned warehouse with the three puncture wounds to the soft palate — a trademark of the shape-shifters — the Fringe team investigates the evidence as well as the motives of mastermind Newton. Upon discovering a shape-shifting embryo, Walter returns to the lab to conduct further analysis, and Olivia and Peter head to Massive Dynamic for answers. Meanwhile, Peter reveals a family secret to Olivia as Walter struggles to recall what Newton knows about "building a door".