2036

"Letters of Transit" is the nineteenth episode of the fourth season of the Fox science-fiction drama television series, Fringe, and the series' 84th episode overall. It is set in the future, where the Observers have taken control of human society. In 2036, two FBI agents fight to free their world of the Observers by finding the amber-encased bodies of the original Fringe team. The episode's premise is subsequently built upon as the key setting of the show's fifth and final season.

The episode was co-written by showrunners J.H. Wyman and Jeff Pinkner, and consulting producer Akiva Goldsman. Executive producer Joe Chappelle served as director. While some critics wondered how the episode related to the overall series, actor John Noble has explained that "Letters of Transit" established the template for the fifth season. It featured guest appearances by actress Georgina Haig and Lost veteran Henry Ian Cusick.

The episode first aired on April 20, 2012 in the United States, and was watched by an estimated 3.03 million viewers. Television critics praised the riskiness of the episode premise and the actors' performances while also expressing doubt about its place during the season. The episode was nominated for the 2013 Hugo Award for Best Dramatic Presentation (Short Form).