When Lister and Kryten developed the triplicator to increase their supplies, they accidently copied the entire ship and then caused it to explode. Two versions of Red Dwarf were created and the Dwarfers had to seek out whichever ship was the superior, so that they could find a working triplicator and reverse the procedure. They only had an hour to do this, as that was how long triplicated material could exist before disintegrating.
After visiting the "High" Red Dwarf and locating the triplicator, Kryten realised that it had only half the required components. They had to go to the other ship and search for the second triplicator. Lister insisted that they should keep their eyes peeled, since the crew of that ship would be the worst kind of people.
The ship was filthy, covered with grease and cluttered with junk. Most of the equipment aboard the ship was decayed and malfunctioning. The sleeping quarters were a mess, littered with rubbish and containing everything that Kryten considered base and soul-destroying: Gore movies such as "Revenge of the mutant splat-gore monster" and "Die screaming with sharp things in your head!", weapons magazines, terrible music like "Hammond Heaven", "Karaoke Krazy" and "Peter Perfect plays tuneful tunes for elderly ladies", whilst the fridge contained sickening foodstuffs: Toastie Toppers, cinema hot dogs and sweaty kebabs. They took the triplicator, which the Lows had no use for, and set it up.
The crew of this vessel were every bit as unpleasant as Lister suspected. His own counterpart, a leather clad cowboy with one eye and a high pitched laugh, shot the High Kryten and Cat before blowing them up with a grenade. The Low Cat was a sabre-toothed savage dressed in skins, while Kryten's double was a greasy, clapped-out maniac. Lister tried to escape but ran into the Low Rimmer, a creepy transvestite who wielded a holowhip and threatened to do unpleasant things to Lister. They captured him and fitted him with a spinal implant, with which they could control his actions.
They first made him injure himself for their amusement, before making him eat a tarantula. They explained that they had to steal Starbug and escape their malfunctioning ship. They made him kill the High Lister and Rimmer, before moving on to his own shipmates. Fortunately, Lister was able to warn them what was happening so that Kryten could chloroform him.
As they tried to leave in Starbug, they noticed that the decay from the Low Red Dwarf was contagious, making the magnetic coils from Starbug's engines depolarise. Employing emergency power, Starbug took off and escaped the Low Red Dwarf, despite Lister's spinal implant still making him try to kill The Cat. When the two versions of Red Dwarf were amalgamated to reform the original, Lister was still being controlled by somebody. The Cat heard a high piched giggle coming from the cupboard and shot the Low Lister who had stowed away (RD: Demons & Angels).