Kate and Ben take a personal interest in a prison mediation and find they have feelings for each other. Leo persuades Lauren to take a case on his behalf.
The Fringe team on both sides fight a common cause and developments are made regarding the Cortexiphan children.
While Olivia and Lincoln try to return Peter home, they try to cope with the looming threat of the transparent shapeshifters. Meanwhile, a traitor is revealed and an old enemy emerges from the shadows.moreless