Of all the Mrs. Flood theories circulating online, Doctor Who season 15 should avoid confirming one in particular. Since Russell T. Davies’ return as Doctor Who showrunner, Britain’s most iconic sci-fi series has been swimming in unsolved mysteries. Heading into Doctor Who season 15, however, the most pressing question undoubtedly concerns Mrs. Flood. Appearing initially as Ruby Sunday’s harmless neighbor, Anita Dobson’s character first sparked suspicion when she broke the fourth wall to utter the word “TARDIS.”

The clues kept coming, and Doctor Who season 14 ended with Mrs. Flood dressed as Romana and promising troubling days ahead for the show’s titular Time Lord. While the most prevalent Mrs. Flood theories have her pegged as a member of Doctor Who‘s Pantheon, other predictions are more outlandish. Some hints point to Mrs. Flood being an older version of Anita from Doctor Who‘s 2024 Christmas special, while some speculate a connection between Mrs. Flood and Clara Oswald. While anything is possible, revealing Mrs. Flood is secretly the Doctor’s granddaughter, Susan, is something Doctor Who should avoid at all costs.

Why Doctor Who’s Mrs. Flood Being Susan Is A Popular Theory

The Doctor’s Granddaughter May Be Hiding In Plain Sight

Susan’s ambiguous status makes her ideal fodder for Mrs. Flood theorists. The Doctor’s granddaughter made her last canonical appearance when she left the TARDIS during the First Doctor’s era. Susan was abandoned on Earth after falling in love with a mortal, and while the original companion later resurfaced in Big Finish audios and other wider Doctor Who media, she and the Doctor have never properly reunited onscreen. Ultimately, therefore, anything could have happened to Susan after parting ways with her grandfather, and there is an undeniable logic in the idea that she secretly followed the Doctor’s adventures after her human husband died

The theory would also resolve most major questions currently surrounding Mrs. Flood. Flood could be an older version of the same Susan regeneration from the First Doctor’s era, or could just as easily be a later iteration. Susan was last spotted on 22nd-century Earth, but being a Time Lord makes it entirely plausible that she found some way of moving through the Time Vortex without the TARDIS.

The grandchild connection perfectly explains why Mrs. Flood is so interested in the Doctor, while her grandfather’s refusal to visit would account for the note of bitterness in Mrs. Flood’s voice whenever she drops her friendly facade. The fact that Mrs. Flood has worn the same outfits as past Doctor Who companions could be a clever nod to Susan’s status as the show’s very first companion, and might again hide a touch of jealousy over how many times her grandfather has recruited fresh companions instead of keeping the promise he made to see his own flesh and blood again.

Also important to consider is that Doctor Who made two direct references to Susan across season 14’s eight episodes. Firstly, the Doctor admitted to feeling fearful over the thought of seeing his granddaughter again, and secondly, Ncuti Gatwa’s character wrongly believed Susan Twist was his Susan in disguise. The recurring Susan motif in Doctor Who season 14 could certainly be intended as an indication that the real Susan is on her way.

Susan Returning As Mrs. Flood In Doctor Who Season 15 Would Miss The Point

Only One Actor Should Be Playing Susan

Doctor Who season 15 revealing Mrs. Flood as Susan may check out logically, but would represent a disappointing answer to the long-running mystery. The appeal of Susan returning to Doctor Who is largely down to the prospect of seeing Carole Ann Ford reprise her role. Ford has been ever-present on the periphery of Doctor Who over the decades, recently starring in the 2020 Big Finish audio series “Susan’s War.” More importantly, Ford has publicly declared her interest in a Doctor Who comeback several times – even as recently as October 2024.

All while Susan’s original actor is waiting for Russell T. Davies to call, casting another actress in the role could only be counterproductive. All the nostalgia and uplifting joy that would come from seeing the Doctor and Susan together in 2025 would be washed away entirely if Anita Dobson replaced Carole Ann Ford. The return would feel hollow, meaningless, and almost like a cynical attempt to obscure a character’s true identity for the sake of creating mystery, sacrificing the impact of Susan’s modern debut in exchange for generating more hype over Mrs. Flood.

The Doctor’s ever-changing face is an intrinsic necessity of Doctor Who, but companion returns are just as intrinsically tied to the actors who played them. Ian Chesterton’s brief cameo in “The Power of the Doctor” would have been redundant with a different actor. Exactly the same is true for Sarah Jane Smith in “School Reunion” and Jo Grant in “The Sarah Jane Adventures.” Revisiting those Doctor Who companions worked only because the classic actors agreed to take part, and that stipulation applies doubly for Susan, despite her status as a Time Lord.

Mrs. Flood Works Much Better As A Doctor Who Villain, Not An Ally

Doctor Who Doesn’t Need Another Disappointing Reveal After Ruby Sunday’s Mother

Beyond just the recasting issue, Doctor Who revealing Mrs. Flood as Susan would land awkwardly after season 14 brilliantly teased Flood’s hidden sinister side. When Mrs. Flood foreshadowed Sutekh’s arrival in front of Cherry Sunday, she briefly carried the presence of an evil, ominous force, delightfully instilling fright into her poor, shaking neighbor. When Flood later warned viewers that the Doctor would be denied a happy ending, she exuded a gleeful, menacing aura worthy of a Brothers Grimm witch, deliciously sparking interest for season 15.

Mrs. Flood feels like something powerful, threatening, and if not outright malevolent, then certainly an entity worth having nightmares over. All of that eerie teasing would feel like pointless misdirection if Doctor Who season 15 eventually unveiled Mrs. Flood as Susan, the Doctor’s loving and completely harmless granddaughter. Russell T. Davies has planted the narrative seed that a woman of unimaginable power and unknown purpose has been watching over the Doctor’s adventures in secret for a very long time. That premise is as intriguing as it is compelling, and has enough substance to form the very backbone of Doctor Who season 15.

No matter how much emotion and happiness Susan’s return could elicit, Doctor Who would be throwing a potentially great villain down the drain if Mrs. Flood and the Doctor’s granddaughter were the same person. Modern Doctor Who has a relatively poor record of creating fresh recurring villains, and still relies on the novelty of familiar foes like the Daleks, the Master, the Cybermen, and, more recently, the Meep, the Toymaker and Sutekh. Mrs. Flood has all the ingredients needed to become a Doctor Who villain for years to come, and merely using her as a cover for Susan would hurt Dobson’s character just as much as it would Carole Ann Ford’s.