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 alternate world's shape-shifters - the Fringe team investigates the evidence as well as the motives of mastermind Thomas Jerome Newton (guest star SEBASTIAN ROCHE). 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."