Lister awakens with amnesia and Kryten explains that he's been in Deep Sleep aboard Starbug for the past 200 years. When Rimmer and Cat both recover from their hibernation, Kryten updates them on the situation. Red Dwarf has been lost and they have been chasing the ship's vapour trail ever since. Now there is a good chance of recovering Red Dwarf at last by heading through an asteroid belt that the large mining ship is forced to circumnavigate. However, the belt turns out to be a spaceship graveyard inhabited by Psirens, shape-changing GELFs who lure unwary travellers to them and suck out their brains.
Cat is almost lured by two attractive women and Lister sees Kristine Kochanski, who tells him that she has two children, Jim and Bexley, that are his. Following another illusion Starbug crashes onto an asteroid and Lister has to blast the front landing gear out, but is tricked twice while on the surface: once by an attractive woman, then by a Psiren masquerading as Kryten. Lister manages to get back on board Starbug safely. However, the airlock monitor fizzes on again and a second Lister appears on the screen. To determine who the wrong Lister is, the crew ask them to play guitar, which Lister does poorly but the Psiren does extremely well. They have found their imposter and blast it away. However, as Lister gets suitably upset by their accusations that he is a poor guitar player, the Psiren has disappeared.
A trail of yellow Psiren blood leads to the engine room. Lister and Cat stay behind to deal with a meteor shower, while Rimmer declines the offer to help, leaving Kryten to follow the psiren blood trail alone. When Kryten finds the Psiren it changes into Professor Mamet, his creator. With no choice but to obey her commands, he climbs into the waste compactor and starts it up. Lister, Cat and Rimmer quickly appear to find Kryten's psi-scan and bazookoid, abandoned on the floor. Rimmer suddenly fades out as his hologramatic light bee battery runs flat. Now just the two of them, Lister and Cat walk up to the Psiren disguised as a vending machine. As they are attacked by the Psiren, Kryten, now cube shaped, waddles over to the edge of the walkway from the deck above and crashes down on top of it.