The discovery of a man over fifty who Markus recognises changes the lives of the residents of Thunder Mountain forever.

Kurdy and Jeremiah are tracking a group wearing protective suits said to be abducting people. When they catch up with them, all but one escape by helicopter. He appears to be at least fifty years old. They take him back to Thunder Mountain, where Markus recognises him as Major Quantrell, controller of Thunder Mountain at the time of the Big Death. It transpires he is from Valhalla Sector; they are preparing to come out and take over the world. Six helicopters bear down on Thunder Mountain, but when Quantrell is killed, they hesitate for a moment and then turn back. Knowing they have passed the point of no return, Markus decides it's time for Thunder Mountain to be more proactive.

Major G Quantrell was the de facto commander of Thunder Mountain due to the death of his superior officers. His intention was to seal off Thunder Mountain, but when he discovered the disease had got inside, he fled and was picked up by a helicopter that took him to Valhalla Sector.

Markus's parents were Dr Sean and Jean Alexander. They died together just outside Thunder Mountain.

Markus was a proficient computer hacker in his adolescence.

We discover that Meaghan's full name is Meaghan Lee Rose.

Lee Chen has a contact outside Thunder Mountain who is aware of Quantrell. This contact is the long-haired man who delivered the warning/blessing to Jeremiah at the start of "The Long Road". Lee lets him into Thunder Mountain, where he follows Jeremiah. He gives his name as Ezekiel, and claims to be Jeremiah's brother, though it is likely he means this figuratively. Later, he gains access to the quarantine area where Quantrell is being kept and kills him by turning on the emergency air evacuation.

"Nothing's the same anymore." - Jeremiah (Commander Sinclair said the same thing in "Chrysalis", the first season finale of Babylon 5, also scripted by Straczynski).

Markus: "They're all gone, but you're still here. Why?" Quantrell: "Clean living."

Valhalla Sector's manifesto, as stated by Quantrell: "We're coming out. That's right. We've been waiting - biding our time. Now we're just about ready to move. And when we do, we're going to build a world based on power. Anybody doesn't like it, we'll push them aside or leave them behind. Because we've got the knowledge. We've got the technology. We've got the guns. And we've got the will."

The moment something inside Markus snaps: "You want a war? You want a war, Jeremiah? Swords into ploughshares, man. You want a piece of flesh, I want a piece of flesh, all God's children want a piece of flesh. You want a war, Jeremiah, you want a war? You got a war."

Kurdy, after listening to Markus talk about the Black Death and the Renaissance: "It's a cool story, but I don't think it really answers 'Are you OK?'."

Markus's phrase "swords into ploughshares" comes from Isaiah, Chapter II, verse 4: "They shall beat their swords into ploughshares, and their spears into pruning-hooks; nation shall not lift up sword against nation, neither shall they learn war any more" (Authorized Version). Jeremiah and Ezekiel are also books of the Old Testament, of course. "Piece of flesh" is likely an allusion to the "pound of flesh" owed by Antonio to Shylock in Shakespeare's The Merchant of Venice.

See the previous episode for a discussion of GPS.

During a flashback sequence, Quantrell likens Meaghan to "Typhoid Mary", the nickname given to Mary Mallon, an immigrant to the U.S. from Ireland. The main point of comparison is that Mallon was a "healthy carrier" of typhoid fever, possessing the disease and able to spread it to others but not suffering from its effects. She was tracked down when a series of homes where she had worked as a cook suffered outbreaks of the disease. Mallon always denied that she was a carrier, pointing to private medical evidence that found no traces of the disease. Nevertheless, she was isolated in a cottage on North Brother Island. Although not imprisoned in such a small space as Meaghan, she did spend a stretch of 23 years there before her suffering a stroke caused her to be moved to a hospital. She died a few years later in 1938.

Quantrell claims he has a GPS beacon chip surgically implanted. It appears he is telling the truth, as the helicopters seem to detect his death.

The belief at the time of the Big Death was that it was transmitted via bodily contact. Dr Alexander also says "stage two infection leads to periodic blackouts [and] dementia."

"My fathers say hello. Both of them," says Ezekiel to Quantrell. Possibly one of the fathers he refers to is Jeremiah's, hence his cryptic claim that they are brothers, in which case, he is still alive and probably also at Valhalla Sector. Further evidence for this theory comes when Quantrell recognises Jeremiah's name.

Both Ezekiel and Lee Chen's personal loyalties are under question. Lee may be a straightforward spy for Valhalla Sector, but Ezekiel is more mysterious. Who benefits from Quantrell's death? In the short term, Thunder Mountain avoids a frontal attack. Does he have orders to protect Jeremiah?

Given that Thunder Mountain was designed to withstand a nuclear blast, what does Valhalla Sector hope to achieve by sending helicopters, however heavily armed? Perhaps they expect Lee to let them in. Alternatively, given his "tin-opener" reference, Quantrell may believe Valhalla Sector has the means to override the key-card security. Of course, it could be a bluff to pressure Thunder Mountain into releasing Quantrell before he gives away any information.

Wow! A pivotal episode that feeds us with a lot of information but in doing so, gives the show's format a fresh impetus by forcing Thunder Mountain to take a more proactive approach now that the antagonists are starting to move out of the shadows. The twin storylines of then and now inform each other and counterpoint neatly to give a richness and texture to the drama.