The episode is a found footage video engineered and narrated by Gagan Rassmussen (Reece Shearsmith), a crew member of a space station orbiting Neptune in the 38th century.

The viewer is addressed by Gagan Rassmussen, a researcher aboard Le Verrier Lab - a space station in orbit around Neptune in the 38th century - through a glitch-filled video transmitted across the Solar System.

Aboard Le Verrier, the four soldiers, Nagata, Chopra, Deep-Ando, and 474, discover the station empty save for the Twelfth Doctor and Clara; passing themselves off as assessors.

The Doctor suspects that Morpheus has transformed the rheum in the corner of the eye into a carnivorous lifeform which digested the crew.

Rassmussen explains why he wanted to ensure that the video the viewer is watching was seen by others, as its glitches contain the Morpheus signal and will allow it to spread.

[3][4] According to writer Mark Gatiss, the Doctor's mention of "the Great Catastrophe" that befell humankind is referring to the collision between the Earth and the Sun described in the Season 21 serial Frontios.

[citation needed] A new title screen specially designed for this episode was shown instead of the usual opening sequence, the first such instance in the show's history.

The website's consensus reads "Doctor Who's effective horror elements and unexpected cliffhanger save 'Sleep No More' from being a gimmicky found-footage episode.