[3] Written by Rob Grant and Doug Naylor, and directed by Ed Bye, the episode has the crew fighting a shapeshifting, emotion-stealing creature.

A non-human life-form with shape-changing properties escapes from a waste pod floating in space and gets aboard Red Dwarf.

Although Holly (Hattie Hayridge) detects it, despite scepticism by Arnold Rimmer (Chris Barrie) that it's a false alarm, the creature attacks Dave Lister (Craig Charles) while he is having a meal.

As Rimmer and Cat (Danny John-Jules) wait for him to recover in the Medical Unit, Kryten (Robert Llewellyn) and Holly reveal the creature to be a man-made genetic mutant called a "Polymorph", designed to leech off its target's negative emotions, revealing that when Lister suffered immense fear when the creature attacked, it drained him of it and has now left him all too eager to face any danger.

As the group leave the cargo decks, they are unaware of a second Polymorph having boarded the ship from the same waste pod floating past Red Dwarf, which follows them, mimicking Lister's appearance.

[citation needed] Director Ed Bye drew inspiration for the look and design of the episode from watching the 1979 film Alien just before shooting began.

[10] The newly introduced Bazookoids provided more video effects as two heat-seeking laser bolts were fired and ended up chasing the Cat.

The episode was originally broadcast on the British television channel BBC2 on 21 November 1989 in the 9:00pm evening time slot,[8] and was well received by fans, many considering it to be the series' best.