Two teenagers turn up dead and evidence indicates that shapeshifters have borrowed their forms for some special mission. While the Fringe team tries to track them down, Peter grows increasingly suspicious of Walter's secretive behavior.

The story alternates to the Fringe Team "over here" where they investigate a mystifying case that people are discovered in a trance-like state that ultimately leads to their death. The unlikely suspect: a mysterious box. As Peter and Walter collaborate to study its properties, alternate Olivia presses on and turns up the heat on an unsuspecting Peter. Meanwhile, key information about the future is revealed when Walter and Nina meet at Massive Dynamic for the emotional reading of the last will and testament of William Bell.

The dying Observer comes to see Walter and Peter, who must take extreme measures to learn what secrets he hides and determine if he knows where Olivia is. Meanwhile, David Robert Jones tries to force Olivia to use her cortexiphan abilities by torturing Nina.

The Fringe team is running out of time to save the world. As Peter, Olivia, Astrid and Walter scramble to tap into a key piece of the puzzle to defeat the Observers, they enlist the aid of Nina Sharp who conjures up a plan.