While going through Kochanski's personal things, Lister finds a photograph of the two of them getting married, an event which clearly never happened, Lister gets to thinking about how this picture could exist. Recalling something, he reads Rimmer's diary entries and there finds one describing a time when Rimmer thought he saw his own head pop up through the table and say that (the head) came from the future to save his (Rimmer's) life, which Rimmer himself (in the diary entry) took to be a hallucination.
Following directions in the diary, the gang head down to deck 16 and, there, find an unnoticed stasis leak, which can be used to transport them back to the past, a short while before the crew all died.
Because they can't bring anybody back to their time, Lister and Rimmer fight over who they should convince to go into the other stasis booth (Lister himself being sent into the other). Lister wants to save Kochanski and Rimmer obviously wants himself.
While Rimmer goes back to convince himself, Lister and Cat find Kochanski at a hotel, but she is already married. Kochanski invites them in and Lister discovers.....Himself! A future version from 5 years in the future, who has found another way to go back in time.
After the meeting, they all return to the past-Rimmer and past-Lister's quarters where the past-Rimmer promptly tells them all to go away.moreless