The team investigate the case of a man who can project electricity... and is at the center of a series of strange deaths involving electricity.

The team is called in to investigate why a man jumps out a window because he thinks he's being attacked by butterflies. Olivia gets some breaks in solving the case from her former partner and that she is so desperate to rid herself of him that she demands to go back into the tank. Meanwhile, some former friends and current foes of Peter find out that he's back in Boston.

The team is called in on a bank robbery similar to other robberies in the area but this particular bank has the thief embedded inside the steel wall of the bank. Somehow the thieves have found a way to defy the law of physics. Walter thinks they're after something of his. As the investigation deepens it all comes to a head when the thieves ambush one of the team.

Just seconds before a building is demolished, a mysterious mute child that has been living alone underground is discovered. When the FBI's Fringe Division investigates, the boy forms an unspoken connection with Agent Olivia Dunham. Meanwhile, an especially gruesome serial killer resurfaces and showcases his "artistry" by displaying his work publicly. As the boy gradually assimilates into a new environment, Olivia and the team must race against the clock to prevent the mad man from causing further massacre.