While exploring an uncharted area of Deep Space, the Dwarfers encounter a ship of Simulants, who want the Casket Of Chronos, which allegedly contains one of their brethren's spirit, in return for Rimmer, who they briefly take as their hostage. Afterward, Rimmer reveals that they were lying - they're actually Expanoids, and they intend to use the device as a Time Machine to change the past. The Dwarfers thus pursue them by time-surfing on their slipstream.
Approaching Earth, Starbug (plus Kryten and Rimmer) is shut down by an EMP and crashlands. Lister manages to get everything rebooted, then he and the others make it to a township full of both people and technology which doesn't correspond to anything in Kryten's database. As it turns out, it's 1952, and the Expanoids have used the opportunity to ban technology so that they can enslave humanity. With the help of a dying man, they are led to the Lady Be Good Club with a strange device. There, with the help of a woman called Harmony de Gaultier, they find that the device is something called a capacitator, a device needed to destroy the Expanoids. However, she doesn't know how to put it together, so the Dwarfers go to find one of the few people who can do it - a man who they believe to be Albert Einstein. Unfortunately, it really is a random hobo called Bob. Oh, and everyone gets busted by the Expanoids. Luckily, Bob figures it out and Harmony sends the signal to wipe them all out. Lister is given an opportunity to stay on Earth, but as Lister is unwilling to lose Kryten (and Rimmer doesn't want to die), everyone returns to their original time and place. Lister concludes that humanity should not be as reliant on technology... having Kryten clean him up.
This episode includes examples of:
- The '50s: The Dwarfers travel back in time to an alternate 1952.
- Achievements in Ignorance: Despite the fact he was selected in a case of mistaken identity, Bob the Bum manages to assemble the device needed to destroy the Exponoids and their anti-technology field.
- Alternate Timeline: The Exponoids create one where technology and science is prohibited during the 1950s. Consequences are that any necessary technology is replaced with Steampunk, scientists become illegal and must study together in secret, and several famous scientists and inventors live different lives, most becoming drunks. The Dwarfers are eventually able to defeat them though and get time back on track.
- Anachronism Stew: Justified since this is set in an Alternate Timeline, but it's mentioned that Einstein and Edison are both drunks now with the former having some sort of theory about some string while having achieved nothing. Albert Einstein's Theory of Relativity was first published in 1905 while Edison is presumably Thomas Edison, who in real life passed in 1931. A possible explanation is that Kryten was wrong and instead of years, the Exponoids arrived decades earlier.
- Cliché Storm: Lampshaded when a bunch of evil Exponoids use Time Travel to conquer the Earth's past, and Lister calls them horribly cliché. This continues later in the episode (paraphrased):Exponoid: So, We Meet Again!
Lister: You really don't mind a hackneyed old cliche, do you?
Exponoid: I think we are not so different, you and I.
Lister: Now you're taking the smeg. - Does This Remind You of Anything?: Doing science is outlawed, and it's played like 1920's alcohol Prohibition in the US.
- Mistaken Identity: The character that the Dwarfers believe is actually renowned astrophysicist Albert Einstein turns out to be just an ordinary crazy homeless guy called "Bob the Bum" who simply looks like Einstein.
- Mundane Utility: The Dwarfers have been using the Casket of Chronos to prop up their pool table on Starbug. They intend to keep using it for that purpose even after they learn of the device's time travel capabilities.
- Not-So-Well-Intentioned Extremist: The Expanoids claim to be helping humanity, then moments later admit to killing people for fun.
- Priceless Paperweight: The Dwarfers didn't know what they found, and were using the Casket of Cronus to balance a wobbly pool table.
- Steampunk: It's shown that cars have gone in this direction in the alternate world.
- Taught by Experience: The Dwarfers are determined to get back the McGuffin from the Exponoids, but not so they could use its time travel abilities themselves. They've learned the hard way of not messing with time travel, after all.
- Troubling Unchildlike Behaviour: According to Lister, he was hot-wiring and stealing cars at the tender age of seven.
- Whole-Plot Reference: The idea of sociopathic robots changing Earth's past so that they can enslave humanity and the Dwarfers having to stop them references the film Star Trek: First Contact, a connection strengthened further by the fact that, much like Captain Picard in that movie, the Dwarfers dress in 1920s gangster style.
