Searching for a new head for Kryten (which exploded due to an incident involving ketchup and lobster), the crew encounter a rogue simulant on a deserted ship. The simulant kidnaps Kryten and commissions one of his own droids, Able, to fix him up. But Kryten and Able discover they're brothers, the same model, and Able helps Kryten escape. But not before Kryten discovers a disturbing secret about his creation...
- Kryten is preparing a surprise feast for the crew, it's the anniversary of when he was rescued from Nova 5 and is serving up lobster taken from the stasis pod of a ship, the SS Centauri. Kochanski has other intentions, taking Lister and Cat into the artificial reality suite and taking them on an educational course through a simulation of Pride and Prejudice. They say they'll eat in a few hours and invite Kryten to join them, Kryten is dispirited the anniversary is delayed.
Lister, Cat and Kochanski enter the simulation and interact with the characters, Kryten enters the simulation in a fury and kills off some of the characters through stealthy means, then interferes a tea picnic with a T-72 Soviet tank. The others return to reality for the dinner, Lister asks for some ketchup on his lobster, Kryten's head explodes at breaking point. Lister and Kochanski refit a new head and when Kryten is activated he explodes again. They use up all the heads and still can't fix him, Kochanski suggests flying to the SS Centauri for spare droid parts, on board they find the presence of a rogue simulant, Kochanski believes they can negotiate with him under the guise as GELFs, Kochanski and Cat disguise themselves as GELFs with Lister as a slave, they board the ship and convince the sim to hand over spare series-4000 heads.
Back on Starbug they find the ship has been looted and Kryten has been stolen, his body is taken aboard the Centauri by the sim's accomplice, another GELF, the sim has another series-4000 droid working as a slave named Able, he is a junkie addicted to a droid exclusive drug named "Otrazone."
He fixes Kryten and introduces himself, Kryten is taken aback by his drug habit and calling Kryten "bro", they are technically brothers as they are the same model. Starbug follows the Centauri which engages warp speed and flies from them, Kochanski advises a full turn which gets the Centauri chasing them, the sim, his GELF ally and his droid prisoners teleport on Starbug where a stand-off occurs. The sim tells Kryten of a locked file in Kryten's CPU and gives him the password, Kryten access it and discovers something disheartening. Able untwists his head and stuns the GELF long enough for Lister to knock out the sim and shoot the GELF, the droids are taken on Starbug.
Lister sees Kryten looking sad and asks what he discovered, his creator, Professor Mamet was to marry a bio-engineer named John Warburton, he jilted her, so she created a robot as a caricature of him, Kryten and the series 4000 are modeled on him. Lister admits he asked Able the same thing, which is what turned him onto Otrazone, Lister notices a box on Kryten's lap, he calls it a "nega-drive" a box filled with all his negative emotions. Lister assures him he's not a joke anymore, he's changed for the better.
They interrupted when the sim follows them, Starbug is forced to hide in an asteroid belt until safe, Able goes to the cockpit with the urge for another hit and faints on the controls, starting the engines, the sim finds them and opens fire. Able is carried to the quarters where Kryten scolds him and seals the door. Starbug can't shake off the sim, Able boards an escape pod with the nega-drive and fires it at the Centauri.
The effects of the drive make the sim destroy the ship in a fit of negativity, the explosion sends Able's pod on a crash landing on an asteroid, Kryten asks for permission to perform a proper burial.
The whole crew revisit the Pride and Prejudice simulation for a curry banquet for Kryten's anniversary, the other characters enjoy the food, but a bug in the program makes the food too hot for the Starbug crew.