Jeremiah is finding catching up with his father very awkward, and Theo is having second thoughts about her baby. Libby and Erin respectively come to the rescue.

Libby has been helping Thunder Mountain create a communication system to link up the members of the new alliance.

More of what Wily said is confirmed in this episode, such as Devon wanting to make public the evidence that the US Government were responsible for creating the Big Death virus. Devon expands on this by saying that he was caught breaking into his own office while Jeremiah's mother waited in the car. They were both taken as prisoners to Valhalla Sector, and the base was locked down for six months. Also there was Paul Weil, creator of the virus, becoming unstable as he saw the devastating effects of his work. He said he would create a diversion allowing Devon, his wife and Paul's son to escape; what they didn't know was that he intended to create the diversion by committing suicide. Jeremiah's mother was killed in the escape attempt.

Thunder Mountain has a functioning gymnasium.

Devon plans to return to Valhalla Sector to bring it back on-line to help the Alliance.

Jeremiah has still been writing letters to his father and burning them, even though he knows his father is alive.

Devon wrote letters to be given to Jeremiah should anything happen to him. Libby gives them to Jeremiah. She also says she memorised their contents in case Valhalla Sector found them.

Jeremiah's mother's name was Mary.

Devon says Jeremiah was very quiet and serious as a child.

Ezekiel was Paul Weil's son. His real name was Simon.

Theo is having second thoughts about keeping her baby - she worries that the child may not have a good upbringing, partly because she doesn't think she knows how to be a good mother. She eventually decides to keep it.

"When you don't have TV or the Internet, you spend a lot of time making babies." - Theo

Devon says Paul was "the kind of guy who re-sequences ribonucleic acid in his head for fun."

"I killed the world… what I discovered cannot be used to terrorise mankind again." - Paul

Theo: "It's gonna be Theo and Leo, or Theo and Cleo - and where we walk, mountains will tremble." After which Markus mutters, "it could be worse - it could be twins."

The "previously on Jeremiah" sequence of clips that open this episode plays an interesting little trick on the audience by including material (Devon saying to Jeremiah, "Ezekiel's dead… Do you know how Ezekiel got his name? He wasn't born with it. He took it on after his real father died") that has not been used before in the show. While it's possible that the dialogue was recorded for "Letters From the Other Side" and never used, there is also a shot of Ezekiel's father (see right) that would be unlikely to have been intended for use in a previous episode.

Along similar lines, the flashback sequence first shown in "The Long Road" is now extended to include more of Jeremiah's mother.

Devon implies that Valhalla Sector is 3000 miles from where Jeremiah's family was living before. Given the likely position of Valhalla Sector, there aren't too many places in the US that are that far away, making it likely that they lived in Washington (or possibly somewhere in Canada). With both Kurdy and Jeremiah coming from the west coast, this further underscores the west versus east tone that the series is taking.

Devon says Valhalla Sector sent out drones to take aerial pictures of the world outside. The fact that they took, and he saw, pictures of their house, hint that Valhalla Sector may already have been formulating a plan to find his sons and use them against him.

Will Daniel turn his attention to Valhalla Sector now that Thunder Mountain plan to annex it? It would have some strategic value, as well as whatever military and intelligence resources it has.

If Valhalla Sector was locked down for six months, how did they send out, and receive images from, surveillance drones? Perhaps they were in radio contact with groups outside who could control the drones and send the images back via satellite.

It's also a bit suspect that during the lockdown period they were able to unseal a maintenance route; the events of "Things Left Unsaid Part Two" would imply that once the base is closed down it's not possible to find any way out. However, as the escape attempted failed, perhaps it wasn't possible to get all the way to the surface after all. Alternatively, locking the base down for extended periods such as six months may allow for some relaxation of the policy for maintenance reasons.

Why does Libby lie about the letters to Devon? Perhaps she thinks he'll be angry about her giving them to Jeremiah behind his back. Or maybe she just thinks it would reopen old wounds that are best left in the past.

Great, character-driven stuff, filling in some of blanks surrounding the period immediately following the Big Death, and showing a vulnerable side to Theo. The attempt to thematically meld the two plots together at the end comes across as rather over-egged, but apart from that this is good drama: complex, intelligent, and moving.