The balance of power in Clarefield is shifting, and Theo may not be top dog for long; Elizabeth is sent to investigate, but when she is captured by Theo's gang, it seems there may be a Clarefield spy at Thunder Mountain.

Markus has heard rumours that Theo may have rivals preparing to stage a coup for control of Clarefield. He hoped the new regime may be prepared to form an alliance, and so he sent two members to investigate, including Elizabeth. Unfortunately, Clarefield picked up a transmission between someone in Thunder Mountain and his sister who lives in Clarefield. Rasmussen stages his coup.

Elizabeth volunteered for the mission to Clarefield; as Simon's lover, she felt she had a score to settle with Theo (see "The Long Road"). She and Kurdy become closer at the end of the episode.

Keith was one of the nerds in "The Long Road".

Jacob Rutledge, an electronics specialist originally from Montana, was recruited by Thunder Mountain six years ago aged twenty. He asked for his sister, Deborah, to join him, but his request was refused. He has been in radio contact with her, and she knows of Thunder Mountain. The council eventually decide to sentence him to a year's ban on the use of communication equipment.

Theo says if she had her time over she would "kill a hundred Matthews, a thousand Simons, if it meant protecting my people". She perceptively points out that deciding who the bad guys and the good guys are seems to have always come easily to Jeremiah. She also points out that her ethical stance is similar to Jeremiah's - they're both ready to kill to protect their own - but that Jeremiah considers himself to be more moral than Theo is.

Theo was raped when she was thirteen. She got a chance to shoot her attacker and fled, pursued by a posse.

"You're not exactly alone man, I'm here." "Yeah, like I said, somebody's got it in for my ass." - Jeremiah and Kurdy.

Theo: "Didn't the Big Death teach you anything?" Jeremiah: "It taught me that life is precious." Theo: "That's funny - it taught me life is cheap."

Erin refers to the law of parsimony, more popularly known as "Occam's razor", which traditionally holds that of competing explanations, the simplest is preferable and that when looking for an explanation for an unknown phenomenon, one should proceed from what is already known. The theory is named after William of Occam (or Ockham), a English monk and scholar born in the thirteenth century, who wrote "Pluralitas non est ponenda sine neccesitate" ("Pluralities should not be posited without necessity").

The motto of Clarefield market - "one thing for another" - rather neatly summarises the plot.

Rasmussen has two marks on his left cheek, and Sam has three. Theo has a red streak running down from her right eye and three red marks on her right cheek. Are these signs of rank in Clarefield?

We glimpse a little more of the way Thunder Mountain is ruled in this episode; Markus appears to chair a council of about nine people, including both Erin and Lee. It seems that the group debate an issue and then Markus makes an executive decision. The strain of this is getting to Markus, and he passes responsibility for the decision about Jacob back to the council. Is this the first time in fifteen years that a problem has divided them? What form of judicial system do they normally use, or do they just expel those who break the rules? Expelling someone from Thunder Mountain may not be a good idea given the secrecy of the place - think what Theo would give for what Jacob knows. This helps to explain why they are reluctant to let anyone in until they're sure they can be trusted.

Theo's dig at Jeremiah, "You strutting around up there on your mountain, clucking your tongue at all of us chumps down here below", is a lot more literal than she realises.

Markus says that if the rules of Thunder Mountain are allowed to be relaxed for even one individual then "one day, all of this will come crashing down." This could be prophetic, given that, wherever his loyalties turn out to lie, Lee is as guilty of unauthorised contact with outsiders as Jacob is.

How does Deborah have access to radio equipment? Possibly it was some old technology of her father's - perhaps Jacob made sure it was kept in good repair.

Lots to recommend here - a return visit to Clarefield was overdue, and there's a nice balance between the two connected plotlines, with everyone getting a little something to do. Best of all is the great interplay between Theo and Jeremiah, which compresses philosophy, wit, character background and a little sexual frisson into a handful of simple scenes.