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.
However, the piece is still in storage in the old Massive Dynamic facility on the main island of New York City, tightly controlled by Observers who can read their thoughts, making its recovery difficult.
They are able to make it to the vault in Massive Dynamic, in part due to the inability of the Observers to read Etta's mind, and successfully restore Walter's memories.
They are, however, unaware that they have alerted Fringe division—still led by Agent Broyles (Lance Reddick)—and the Observers to their presence; a coordinated team, instructed to shoot on sight, is dispatched.
Walter is able to lead Simon and Etta to where Peter Bishop (Joshua Jackson), Astrid Farnsworth (Jasika Nicole), and William Bell have been encased in amber.
Leading up to its broadcast, journalists noted that the nineteenth episode of each season of Fringe has generally been its "craziest hour", and anticipated that "Letters of Transit" would be similarly strange.
[7][8] The episode contained a new opening credit sequence that helped set the tone, with "fringe" terms including community, joy, imagination, and free will.
[9] Actor Henry Ian Cusick and actress Georgina Haig guest starred in the episode as a pair of Federal agents.
[10] Cusick stated that most of his scenes were filmed with Haig and John Noble (Walter Bishop), and that the story leaves a possibility for the return of their characters in the future.
Some fans of this type of material will like it anyway because Henry Ian Cusick was such a big star in Lost, but also, this new girl is just full of wonderful energy, too.
"[5] Given guest star Henry Ian Cusick's prominence in Lost, "Letters of Transit" refers to both "The Purge" and "natives", two key elements of that show.
Jeff Jensen of Entertainment Weekly believed these helped set the tone of the episode: "Fringe in 2036 was The Village writ global and under Imperial rule.
"[9] Matt Roush of TV Guide noted that the episode title, "Letters of Transit", alludes to a key element of the film Casablanca.
[14] "At this point, with the end of the series a virtual certainty either this year or next, and the ratings indicating that there's nothing left but hardcore fans, I suppose the producers didn't have much to lose by taking a chance.
Isler concluded that "the core ideas are really good, but the way the new concepts were introduced seems haphazard, and a huge gamble that could turn off all but the most hardcore viewers.
"[15] Tucker's Entertainment Weekly colleague Jeff Jensen commented that he was able to "roll" with some of the less plausible plot details (such as a still existing Massive Dynamic) out of praise for guest stars Cusick and Haig, believing they "worked well in this world."
He wondered how the episode fit into the rest of the season, and wrote "It’s a curious step, and could likely drive even more viewers away from a show that can’t afford to lose them."
But the single episode that introduced this premise was a cool jolt that opened a new front of Fringe mythology and gave us a character that would have a lasting impact, Etta.