Genre: Mystery

Olivia begins to regain her memories of her encounter with William Bell. Meanwhile, the "First Wave" tries to collect the head of their leader, and the traitor makes his move.

When an American officer who served in Iraq blows up in a Philadelphia train station, the Fringe Division investigates and determines that something turned the man into a living bomb. Peter and Olivia travel to Iraq to determine if Peter's contacts can shed some light on the situation.

A highway construction worker is the seventh in a series of mysterious disappearances in Lansdale, PA. The team come to investigate and finds traces of a mysterious paralytic. Meanwhile, Walter tries to send frogs to an alternate reality and Olivia realizes her recent trip has altered her in ways she can barely understand.

An amnesiac Olivia makes her return from the parallel universe, while Walter, Pete, and Junior Agent Amy Jessup investigate the mysterious death of a man found with puncture holes in his palate. Meanwhile, Broyles defends the Fringe Division from a Senate subcommittee threatening to shut the organization down.