Trama

Starbug flies into a Dimensional Tear and the crew meet themselves from an alternate reality where Lister is a hologram and Kochanski is alive. When a GELF ship opens fire on Starbug, alternate Kochanski becomes stranded with no way home.

Lister, Cat and Krytern stumble upon a doorway that leads to another dimension. Where Lister learns he died in the nuclear disaster on-board Red Dwarf and has been brought back as a hologram and Lister's former girlfriend, Console officer Kristine Kochanski was in stasis and survived and Lister discovers the truth about himself.—Daniel Williamson

In 2155 Lister is abandoned as a baby, left in a box under a pool table, a word is written on the side of the box, "Ouroboros", which is misread as "Our Rob or Ross."

On Starbug Lister is getting ready for bed and sneezes out his tooth cap, Kryten comes in with some bed clothes which Lister puts on, a chiffon night gown and bunny slippers, Lister attempts to refit his cap with domestic glue and then flosses, getting the floss stuck in his mouth. Cat comes in with news that something has appeared outside. A rift has appeared in the universe and is heading toward them, they fly into the eye of the storm, a tunnel has appeared in the engine decks, it leads to the void between realities where another universe is connected, an alternate Lister appears, a hard-light hologram, along with Cat and a gold-suited Kryten. In that reality Lister returned to Red Dwarf with his pet cat, which Kochanski discovered, she hid the cat and was found, she was sent to stasis for breaking quarantine regulations, Lister was killed in the radiation leak.

This means Kochanski is alive in that universe, she mentions that one day she would like to have children and the living Lister could be the surrogate father, she gives him a test tube to contribute to, when the rift is attacked by a cruiser, Kochanski falls into a tear in the rift and the living Lister rescues her. She loses consciousness and awakens in Starbug's medical lab at first believing she's in her universe, Starbug comes under attack from the cruiser, it's a GELF ship, the tribe that Lister married into in the previous season. He's demanded to return to his bride, Kochanski gets them to outfox the cruiser with a sudden turn maneuver, crashing the cruiser.

It's going to be a while before the rift reopens and Kochanski can return to her universe, while Kryten is becoming jealous by her presence, he knows Lister has been looking for Kochanski for a long time and he fears he'll be alone, he helps Kochanski get back to her reality as soon as possible. The linkway is reopened and she can leave, before she does Lister gives her the test tube with their baby inside, the only advice he can relay to the child is not to assume it was deserted like he was, she heads back to the linkway giving them a cell phone to communicate transdimensionally. Cat brings back some supplies from the other side, one is a box containing everlasting batteries, the logo is of a snake eating its tail, the symbol and batteries are called "Ouroboros".

The name catches Lister's immediate attention, Ouroboros was the word on the box he was found in, Lister realizes that the test tube baby is himself, he must go back in time and place the baby under the table in the past, he finally discovers who his family really is, he rushes after Kochanski asking the test tube back, the rift is attacked again by the GELF cruiser and the linkway is damaged with Kochanski on the wrong side, she tries to jump but falls into the void, she calls Lister on his phone and offers to stay if he can save her in time, the others rush back to find rescue equipment, a crossbow and rope, Lister saves her in time.

She is brought on Starbug where she's told the linkway is sealed for good, she's going to find a way back regardless. Eighteen months later, Lister travels back to 2155 with his newborn son, he tells him was never abandoned after all, he was put there to create an endless loop, as long as the Lister men are going around in time the human race will never go extinct, he sees the baby goodbye and places him under the table.