Episode 11 - Reciprocity. When the Fringe Team visits Massive Dynamic's assembly of the doomsday device, Walter becomes greatly concerned for Peter's well-being, so he turns to Nina for added brain power to understand the relationship between Peter and the superweapon. Meanwhile, the discovery of a dead body triggers an intense investigation. Walter asks Nina if she can understand the connection between Peter and the doomsday device, while the team visits the assembly of the doomsday device at Massive Dynamic. Meanwhile, a dead body's discovery causes a huge investigation.