The viewer is addressed by Gagan Rassmussen (Reece Shearsmith), a researcher on the Le Verrier Laboratory, a space station orbiting Neptune in the 38th Century. The video is glitchy, but he wants the viewer to see the found footage therein. Communication is lost and a rescue mission is launched from Triton. Four soldiers board the station—Nagata (Elaine Tan), Chopra (Neet Mohan), Deep-Ando (Paul Hyu), and 474 (Bethany Black)—and find it empty except for the Doctor (Peter Capaldi) and Clara (Jenna Coleman), who say they are assessors. They are all attacked by Sandmen, who are humanoids made of dust.

They hide in a lab filled with pods and discover Rassmussen. He is the inventor of the pods, called Morpheus, that send signals to human brains to compress a month’s sleep into a few minutes. These pods are more advanced than those on Triton. The Doctor thinks that Morpheus has transformed the rheum in the corner of the eye into a carnivorous lifeform which has digested the crew.

The gravity shields are powered down so the Doctor can fix them. A Sandman appears to absorb Rassmussen. Chopra, Deep-Ando, and 474 are killed. The Doctor monitors the Sandmen and realises that Rassmussen is making them blind by hijacking the visual receptors in the eyes of the Sandmen and anyone who has used Morpheus.

They escape to the ship, but Rassmussen is alive and traps them in a room with a Sandman. Rassmussen plans to return to Triton and release Morpheus there. Nagata shoots Rassmussen. The Doctor arranges an escape and destroys the gravity shields, sending the station and the ship spinning into Neptune. The Doctor, Clara, and Nagata escape in the TARDIS. Rassmussen reveals himself as a Sandman being pulled apart by Neptune’s gravity. The video’s glitches contain the Morpheus signal, and it spreads.

The title is from Shakespeare: “Sleep no more! Macbeth hath murdered sleep.” The Morpheus machine is named after the Greek god of dreams. Mr. Sandman was sung by the Chordettes in 1954. Those who do not use the Morpheus Machine and sleep for hours and hours are called Rips, as in Rip Van Winkle. Bethany Black (474) is the first openly transgender actor on Doctor Who. 474 is a Grunt, bred for war and tattooed for that reason. Reece Shearsmith (Rassmussen) played Patrick Troughton in An Adventure in Space and Time. The space station is named after Urbain Le Verrier, the French mathematician who predicted the existence of Neptune by its affect on the orbit of Uranus. As a found-footage story, there are no opening credits; they appear at the end. The writer, Mark Gatiss, suffered from insomnia when he wrote the story.