Fringe: Grey Matters

"Grey Matters" is the 10th episode of the second season of the American science fiction drama television series Fringe. The episode was written by Ashley Edward Miller and Zack Stentz, and directed by Jeannot Szwarc. It centered on three mental patients who mysteriously became sane again after shapeshifters from the parallel universe removed a piece of foreign tissue from each of their brains; this tissue is later revealed to have been taken from the brain of Walter Bishop years before. The fringe team of Olivia Dunham, Peter Bishop, and Walter investigate and face a new enemy, Thomas Jerome Newton (guest actor Sebastian Roché), whose purpose is to decipher the missing parts of Walter's brain and find out how to move between universes. The episode features the first scene between Walter and his old colleague William Bell (played by guest actor Leonard Nimoy). At the time, it fulfilled Nimoy's commitment to the show, though he later returned for the season finale. "Grey Matters" first aired in the United States on December 10, 2009 on Fox to mostly positive reviews. An estimated 6.33 million viewers watched the episode, and it received a 2.3 ratings share among those 18–49.