The storyline followed the Fringe team's investigation into a numbers station that mysteriously gave its listeners amnesia, a case that ultimately ties to a doomsday device.
The Fringe team is brought in on a case where several people, part of an online group attempting to decode the information sent by a numbers station, have been stricken with amnesia.
Peter discovers that the rare book shopkeeper, Edward Markham (Clark Middleton), was part of the online group but did not listen that night.
Edward provides his theory of the numbers stations to Peter and Fauxlivia: that it is a signal left by the "First People", an advanced civilization that existed before a mass extinction event.
Later, the crash of a small commuter aircraft is attributed to a similar signal from a numbers station, and when Fringe division identifies the source, they find a second box.
Taking the box to Walter, Peter identifies one of the electronic components as rare, and engages his contacts to find Feller's address from its purchase.
The episode ends in the parallel universe where Olivia, having broken Walternate's conditioning making her believe herself to be Fauxlivia, is told that no further tests are needed.
"6955 kHz" was written by story editors Robert Chiappetta and Glen Whitman, while frequent Fringe collaborator Joe Chappelle served as the director.
Writing for Entertainment Weekly, critic Ken Tucker noted and appreciated that "many key details were provided by characters who don't often serve that function", such as with Broyles and the numbers stations.
"[12] Los Angeles Times writer Andrew Hanson enjoyed the episode's many puzzles and expressed appreciation for the "First People" revelation as well as Walternate's "long con" concerning the doomsday device.
[13] Hanson was skeptical that Peter had not yet figured out Fauxlivia's true identity, but praised Anna Torv's performance ("Anyone who doubted [her] acting chops in the first couple of seasons should be eating their words").
The dialogue was often painfully expository, with liberal doses of ADR to make sure that we viewers didn't miss any of the massive amounts of significant information we need to understand as the story moves forward...And yet the episode was also funky and philosophical in the way I like my Fringe to be, using the plot and even the setting to put across more than just pieces of the series' mythology.
"[2] SFScope's Sarah Stegall believed the episode "start[ed] out interestingly enough", but unlike other reviewers, she was very critical of the First People mythology, stating "This is where my disbelief not only stopped being suspended, it got up and walked out of the room...