Doctor Who 'The Legend of Ruby Sunday': Who is Susan Triad?

Susan Twist as Susan Triad in Doctor Who - The Legend of Ruby Sunday (2024)
(Image credit: BBC)

"There's always a Twist at the end," proclaimed the song and dance routine at the end of "The Devil's Chord." The penultimate episode of this "Doctor Who" season has delivered on that promise. 

Susan Twist, an actor who's had numerous cameos in the latest run of episodes, finally took center stage as tech entrepreneur Susan Triad, in a plotline that has big ramifications for the Doctor (Ncuti Gatwa), Ruby Sunday (Millie Gibson), planet Earth and the universe as a whole. "It is not true that I cast Susan for her name," laughs showrunner Russell T. Davies on behind-the-scenes companion show "Doctor Who: Unleashed. "But the name helped."

Here we explain where you've seen the mysterious Ms. Triad before, how she may (or may not) have ties to a certain Time Lord's family tree, and why her "employer" is very bad news for everyone.

Disney Plus

Disney Plus is now the international home of "Doctor Who." That means that viewers outside the U.K. can watch new "Doctor Who" episodes on the streamer — as well as the three David Tennant-starring 60th anniversary episodes, and Ncuti Gatwa's first full outing as the Time Lord, "The Church on Ruby Road". 

Episodes debut on Disney Plus at the same time they appear on BBC iPlayer.

Who is Susan Triad?

Susan Twist as Susan Triad in Doctor Who - The Legend of Ruby Sunday. (Image credit: BBC)

As well as being a tech entrepreneur and the public face of S Triad Technology, Susan Triad is a genius, a philanthropist and — like Tom Hardy, Kate Winslet and Dolly Parton — a veteran of "Bedtime Stories" on toddler-friendly TV channel CBeebies. According to UNIT (Unified Intelligence Taskforce) agent and former TARDIS companion Mel Bush (Bonnie Langford), she's also incredibly nice.

In "The Legend of Ruby Sunday," Triad is preparing for the global release of new free software with major aspirations. "This is when the whole world is changed by me," she claims, ramping up the hyperbole.

Where have we seen her before?

Susan Twist in Doctor Who - Wild Blue Yonder in 2023. (Image credit: BBC)

It's no coincidence — nor a money-saving exercise — that actor Susan Twist has played numerous roles this year. Much as the words "Bad Wolf" and "Vote Saxon" were teases for the finales of Russell T. Davies's first and third seasons at the show's helm, Twist's prior cameos have been breadcrumbs leading the way to this two-part finale. 

In previous weeks Twist has played:

  • Isaac Newton's housekeeper in "Wild Blue Yonder" (which featured David Tennant as the Doctor)
  • A heckler in "The House on Ruby Road"
  • A Planet Pacifico Del Rio comms officer in "Space Babies"
  • A tea lady in "The Devil's Chord"
  • An automated ambulance in "Boom"
  • A hiker in "73 Yards"
  • Lindy's mum in "Finetime"
  • A portrait on the wall in "Rogue"

Related: Doctor Who companions ranked worst to best

The Doctor also recalls seeing her face on a Sloogman from the planet Sloog (spookily reminiscent of the Borg from "Star Trek"), and a Griffin from the Planet Varsitay.

Triad has no conscious knowledge of these other incarnations, but she has seen them in dreams. The fact she doesn't realize her cosmic importance doesn't mean she can't be dangerous, however — as UNIT boss Kate Lethbridge-Stewart (Jemma Redgrave) puts it, a caterpillar doesn't know it's destined to become a butterfly. 

Why does the Doctor think there might be a family tie?

Carole Ann Ford as Susan Foreman in Doctor Who - The Dalek Invasion of Earth. (Image credit: BBC)

Firstly, there's the fact that S Triad is an anagram of TARDIS — a contrivance that suggests a 95% (and rising) probability that Triad's arrival on the scene is a trap. (This is just the latest in a long line of anagrams in "Doctor Who" lore, including alien-hunting organization Torchwood (Doctor Who), Kylie Minogue's one-off companion Astrid (TARDIS) and the Kaleds (the species that mutated into the Daleks).)

Then, there's Triad's first name: Susan. 

Susan was the name of the First Doctor's (William Hartnell) granddaughter when the show began way back in 1963. Played by Carole Ann Ford, she left the TARDIS behind in 1964's "The Dalek Invasion of Earth", but — beyond her appearance in 20th anniversary adventure "The Five Doctors" — she's barely been mentioned on screen since. 

The Doctor doesn't seem particularly eager for a family reunion, telling Kate Lethbridge-Stewart that he brings "disaster" and that seeing her again might "ruin her". As for the identity of the Doctor's kids? When the UNIT head tries to get her head around Gallifreyan genealogy, the Time Lord says he doesn't have any — "Not quite. Not yet" — explaining that his back-to-front family tree is the "life of a Time Lord." (Of course, this will be no surprise to anyone who recalls River Song's topsy-turvy backstory during the run of Matt Smith's Eleventh Doctor.)

Related: The Doctor Who Doctors ranked worst to best

If she's not the Doctor's granddaughter, who is Susan Triad really?

A new look at Sutekh in Doctor Who - The Legend of Ruby Sunday (2024). (Image credit: BBC)

She's the (seemingly) unwitting mouthpiece of Sutekh, an evil entity that's woven its essence into the fabric of the TARDIS, and wants to bring the "gift of death to all humanity." According to Harriet Arbinger (Genesis Lynea) — the second H. Arbinger (get it?) of the season after Harry in "The Devil's Chord" — "the lord of time was blind and vain and knew nothing" as Sutekh bided its time.

"Did you think I was family, Doctor?" a possessed Susan taunts at the end of the episode.

Has the Doctor encountered Sutekh before?

The alien Sutekh in Doctor Who - Pyramids of Mars Part Three (1975). (Image credit: BBC)

Yes, Tom Baker's Fourth Doctor faced off against Sutekh in 1975 story "Pyramids of Mars." And the deity's return has also been foreshadowed in last year's 60th anniversary specials and throughout the current season. 

Before his demise, god of games the Toymaker (Neil Patrick Harris) told the Doctor that "the One Who Waits" (aka Sutekh) was so intimidating that even he wouldn't challenge it to a contest. The Toymaker's child, music god Maestro (Jinkx Monsoon), subsequently warned that, "The One Who Waits is almost here."

We're speculating here, but Sutekh may also be one and the same as the satanic beast David Tennant's Tenth Doctor found imprisoned in 2006 two-parter "The Impossible Planet"/"The Satan Pit." For one thing, both the beast, and Sutekh's 1975 and 2024 incarnations were voiced by the same actor: Gabriel Woolf.

What's Sutekh's connection with Ruby Sunday?

Ruby Sunday (Millie Gibson) and the Doctor (Ncuti Gatwa) share a look in "The Church on Ruby Road". (Image credit: Lara Cornell/Bad Wolf/BBC Studios)

That's a good question — and one that will hopefully be answered in the season finale, "Empire of Death". 

We do know that Sutekh's ominous cloud of evil has centred itself on the TARDIS, and somehow found its way into the VHS recording of the night baby Ruby was abandoned outside a church. We're guessing Sutekh also has links to the hooded figure sighted in the churchyard.

The Sundays' neighbor, Mrs. Flood (Anita Dobson) — the one with a penchant for breaking the fourth wall — also delivers an ominous threat to Ruby's gran (Angela Wynter): "There's a storm coming. He waits no more." Maybe Sutekh recruited her to keep an eye on Ruby for some diabolical reason? She wouldn't be the first Flood associated with an apocalypse of biblical proportions…

"Doctor Who" streams on BBC iPlayer in the UK and Disney Plus elsewhere in the world. New episodes debut at 7pm ET/4pm PT on Fridays, and midnight on Saturdays in the UK. Our guide to watching new "Doctor Who" episodes explains more.

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Richard Edwards Contributor

Richard's love affair with outer space started when he saw the original "Star Wars" on TV aged four, and he spent much of the ’90s watching "Star Trek”, "Babylon 5” and “The X-Files" with his mum. After studying physics at university, he became a journalist, swapped science fact for science fiction, and hit the jackpot when he joined the team at SFX, the UK's biggest sci-fi and fantasy magazine. He liked it so much he stayed there for 12 years, four of them as editor. 

He's since gone freelance and passes his time writing about "Star Wars", "Star Trek" and superheroes for the likes of SFX, Total Film, TechRadar and GamesRadar+. He has met five Doctors, two Starfleet captains and one Luke Skywalker, and once sat in the cockpit of "Red Dwarf"'s Starbug.