The Eaters of Light

Synopsis

The Doctor and Bill had a disagreement about what happened to the Ninth Legion of the Roman army. To settle it, they took the TARDIS to second-century Scotland, with Nardole along for the ride. Bill went off on her own to find the Legion, while the Doctor and Nardole searched for their remains. Bill found some of the soldiers hiding underground. Thanks to the TARDIS’s translation circuits, she could talk to them. They were hiding from a creature they called a "Light Eating Locust," which was drawn to any light and killed whatever it touched. Meanwhile, the Doctor and Nardole discovered the boneless bodies of the rest of the Legion. They then came across a Pict tribe guarding a stone cairn, waiting for their leader, Kar, who was known as the "Guardian of the Gate." The Doctor got impatient and went into the cairn, which led to an interdimensional portal filled with creatures feeding on a light source. He came back out only seconds later, but more than two days had passed. Kar explained that once every generation, one of their warriors went through the cairn to defeat an "Eater of Light." Because of the invading Roman army, she had let one of these creatures escape to fight them. The Doctor warned her that if they did not get the creature back into the portal and close it, more of its kind would escape and eventually consume the sun and all the stars. Bill led the surviving Roman soldiers away from the creature, and they ended up near the cairn, reuniting with the Doctor and Nardole. The Romans and Picts agreed that their conflict was trivial compared to the larger threat. The Doctor devised a plan to lure the Eater back to the portal during daylight. Once the creature was trapped inside, the Doctor said someone had to stay in the portal until the sun burned out to stop the creature from escaping. Since human lives were too short, he prepared to go in himself, counting on his Time Lord physiology and regenerative abilities to protect him. Bill objected and knocked him down. Kar and the remaining soldiers of the Ninth Legion chose to sacrifice themselves together to stop the creatures, despite the Doctor’s protests. After the portal was closed, the remaining Picts honored Kar’s memory by building monumental stones and teaching crows to say her name. Nardole observed that this tradition continued into the present day.

Production

The episode's read-through occurred on 12 October 2016, and principal photography ran from 2 November to 22 November 2016. In October 2016, Steven Moffat revealed that a writer from the classic series would return for an episode. This was later confirmed to be Rona Munro, who had penned the Seventh Doctor serial Survival, the final story of both Season 26 and the original run. She became the first person to write for both the classic and revived series.

Broadcast and reception

The overnight audience for this episode was 2.89 million, which at the time of broadcast was the lowest overnight figure for any episode of the revived series since 2005, following the previous episode's 3.01 million. Its overnight audience share was 22%. The total consolidated viewership was 4.73 million, also the lowest overall rating for the programme since its 2005 return. It ranked as the twenty-sixth most-watched programme of the week, with a final audience share of 30.3%. The Appreciation Index score was 81.

Critical reaction was generally described as "solid, if flawed." On Rotten Tomatoes, the episode holds a 100% approval rating from 15 reviews, with the site's consensus noting that it highlights the Doctor's most relatable qualities and embeds timely political subtext within compelling drama. Alasdair Wilkins of The A.V. Club awarded a B+, praising writer Rona Munro for skillfully blending the political and the personal, particularly in her portrayal of the Roman army and the soldiers' complexity. He observed that the episode felt like a throwback to an earlier era of the show, as Munro was the first writer from the classic series to return for the modern run. Wilkins noted that criticisms of the prior episode applied here too, given the retro feel, but described the episode as "bizarre" in a positive sense, with a "tremendous, distinctive atmosphere."

Kathleen Wiedel of TV Fanatic gave 3.3 out of 5 stars, calling it a solid story with several enjoyable elements, including Nardole's interactions with the natives, the Doctor's discussion of crows, and Bill's discovery of the TARDIS's translation ability. She commented that when the Doctor declared he would guard the gate, the outcome was predictable—viewers could anticipate that the supporting characters would take his place.