Just one week after Peter Bishop saved the day and was then wiped from existence, the truce between the two worlds remains intact and the two sides are forced to work together. Lincoln Lee joins the Fringe team as they investigate a shapeshifter case that is very personal to him.

Olivia and the others of Fringe division attempt to determine the origin of Peter Bishop, who purports himself as Walter's son who had died as a young boy in the original time line.

Peter's visit to the other side intensifies as the alternate FRINGE division faces off against a formidable new foe in a harrowing race against time.