Lux (Doctor Who)

Plot

The TARDIS fails to return to 24 May 2025 and instead lands in Miami in 1952. The Doctor and Belinda discover a cinema that has been chained shut. At a diner, they meet the mother of one of fifteen people who vanished from the cinema, which still plays movies at night despite being locked. Although racial segregation is the law, the waiter lets them stay.

Inside the cinema, they find that a living rubber hose cartoon character named Mr. Ring-a-Ding is responsible for the disappearances. He is the embodiment of Lux Imperator, God of Light and a member of the Pantheon of Discord. The projectionist, Reginald Pye, runs films for Lux, who uses his power to recreate Pye’s dead wife. Lux has trapped the missing people inside a film reel.

He also traps the Doctor and Belinda, turning them into cartoon characters. They regain their normal forms by feeling sad, which makes them more three-dimensional. They flee into another false reality, where a racist police officer wearing an NYPD uniform wrongly accuses them of violating segregation laws by being in the cinema. They escape through a television watched by Doctor Who fans.

The fans are thrilled to meet the Doctor and believe that destroying the film reels will defeat Lux. They reveal that they are not real and will vanish once the Doctor and Belinda leave, but they urge him to return to the real world and defeat Lux. The Doctor and Belinda escape by burning the film reel; the Doctor hurts his hand but heals it with leftover regeneration energy. Lux steals this energy to create a solid body and leave the theater.

Belinda tries to burn more film reels to cause an explosion, but Pye, encouraged by his wife, sacrifices himself. The explosion lets sunlight into the cinema, causing Lux to expand infinitely until he evaporates into the universe, freeing the missing people. As the Doctor and Belinda depart, Mrs. Flood appears and tells the bystanders to watch the TARDIS dematerialise, saying this show is a limited run that ends on 24 May. In a mid-credits scene, the three Doctor Who fans from inside Lux’s trap critique the episode, realizing they still exist.

Production

"Lux" was penned by showrunner Russell T Davies, who had long dreamed of incorporating a living cartoon into an episode but was previously prevented by budget limitations. Two decades earlier, he had considered a version featuring a hologram instead of full animation for the same financial reasons. The story touches on segregation and racism, elements Davies included to reflect contemporary societal issues and to subvert the Doctor’s typical role as the primary authority figure, though he was careful not to let these themes dominate the episode.

Specific instances include a NYPD officer declaring the cinema “reserved for white folk” and wrongly assuming Belinda is Caribbean. The episode also explores grief, hope, friendship, and sadness. Cultural nods to Rock Hudson and Scooby-Doo’s Velma appear. Davies continues his recent habit of having a character break the fourth wall by addressing the camera directly.

Unusually for the series, a mid-credits scene is included. Meta-commentary on Doctor Who fans emerges: they name “Blink” (2007) as their favorite episode, hint at a possible cancellation, note the episode’s obvious foreshadowing, and mention online leaks. The BBC ident appears on their television screen. Though the three characters—Hassan Chowdry, Lizzie Abel, and Robyn Gossage—claim they are too insignificant for surnames, all are fully named in the credits.

Broadcast and reception

"Lux" landed on BBC iPlayer at 8 a.m. BST in the UK and on Disney+ at midnight Pacific Time on 19 April 2025, with a BBC One broadcast later that evening at 7:15 p.m. BST. Disney managed the episode's release outside the UK.

Overnight figures showed 1.58 million viewers tuned in live, marking the lowest broadcast ratings in the show's history and the first time they dipped under 2 million. That day, it ranked as the fourth most-watched programme on BBC One, trailing behind Britain's Got Talent on ITV1. Over seven days, consolidated viewing numbers reached 3.04 million, climbing to 3.72 million after 28 days.

Critics offered mixed reactions. Robert Anderson at IGN singled out Mr. Ring-a-Ding, the fourth-wall-breaking scene, and the performances of Gatwa and Sethu for praise.

Martin Belam of The Guardian also liked the episode, highlighting Cumming's work and that same meta moment. Will Salmon from GamesRadar+ noted Mr. Ring-a-Ding and Gatwa's acting but felt Murray Gold's score sometimes overwhelmed the dialogue. Adi Tantimedh at Bleeding Cool called it the strongest episode from Davies in his second run as showrunner.

On the other hand, Andrew Blair at Den of Geek praised how Mr. Ring-a-Ding was written but argued the episode felt too similar to "The Devil's Chord," which made it repetitive and weaker. He also found the handling of race ineffective, noting that while the attempt to include the topic was admirable, the Doctor's overly optimistic approach seemed problematic given real-world racism. Vicky Jessop of the Evening Standard took issue with a scene featuring Doctor Who fans, saying it started off amusing but quickly became forced.

Did You Know?

• A novelisation written by James Goss was released on 10 July 2025 as part of the Target Collection.
• The audiobook will be read by Dan Starkey, who previously recurred as Commander Strax.
• The cover of the novelisation was designed by Dan Liles.