Warning: This article includes MAJOR SPOILERS for Doctor Who season 15, episode 6, "The Interstellar Song"!

The Doctor’s first companion and granddaughter, Susan Foreman, appeared briefly in Carole Ann Ford’s cameo in Doctor Who season 15, episode 6. The Doctor’s granddaughter, Susan Foreman, appeared with the original actor playing her. The scenes in question show her as a vision, calling out to the Doctor right before the titular main character freezes to death. Because she asks Fifteen to come find her, it seems that Susan might not have just been a near-death hallucination.

Although the Doctor thinks that she died when the Master destroyed Gallifrey and committed genocide against the Time Lords, Susan might actually be out there, alive and waiting for the Doctor’s help. As such, Whovians have started coming up with theories about how she will return to Doctor Who for real. The ideas range from highly likely to fun but improbable. However, most of them could actually come true, considering Doctor Who’s penchant for silliness. Either way, these are six of the most entertaining theories about Susan’s expected return in Doctor Who.

6 Susan Has Been Captured By The Rani

The Rani Could Kidnap Susan To Hurt The Doctor

The most likely theory that I’ve seen about Susan’s return in Doctor Who season 15 is that the Rani captured her. Mrs. Flood’s regeneration has clearly been following the Doctor and their companions, working towards a plan to bring her enemy “absolute terror.” If she’s looking to hit the Doctor where it really hurts, the most logical choice would be for her to go after the people that the Doctor loves. This means old companions like Donna Noble and Rose Tyler are on the table. Additionally, if she really wanted to make him suffer, she’d go after the Doctor’s granddaughter.

When Fifteen talks about Susan in Doctor Who season 14, they express regret that they didn’t ever go back for her. If Mrs. Flood was somehow listening in on this conversation, it could’ve given her the idea to go after the granddaughter. Susan calling out for help through a vision would make complete sense if the Rani captured Susan before bigenerating in Doctor Who season 15, episode 6. She’d want the Doctor to find her and save her. Mrs. Flood and the Rani would put her life in danger.

5 Susan Survived Earth’s Destruction With The Help Of The 14th Doctor's TARDIS

Susan Could've Escaped Earth Right Before Its Destruction

One of the most peculiar parts about Susan Foreman’s appearance in Doctor Who season 15, episode 6, “The Interstellar Song,” is the fact that she appears to be inside the Fifteenth Doctor’s TARDIS, despite never having stepped foot inside this iteration of the time traveling box. This could just be a coincidence or a result of the Doctor’s psychic connection to the TARDIS. Their mind might have superimposed their granddaughter in a familiar environment. However, one fan theory suggests that she actually is inside a version of the TARDIS that resembles Fifteen’s box – Fourteen’s TARDIS.

While “The Interstellar Song” provided more context about Earth’s destruction, it didn’t say whether people on Earth knew it was coming. Susan might have escaped Earth right before the planet ended on May 24, 2025, using the 14th Doctor's TARDIS. If true, this would explain why she looks like she's inside the TARDIS in the visions. Additionally, she would want the Doctor to come find her since she doesn’t know where they are. The most significant downfall in this theory is that Susan would need to know that the Doctor bi-generated and where to find Fourteen.

4 Susan Is The Mother Of Belinda Chandra

Belinda Chandra's Parents Still Haven't Appeared Onscreen

From the beginning, Belinda Chandra has said she wants to go home to her parents. Although their initial mention could be written off as establishing Belinda’s motivations, Belinda’s parents have become a bit of a Chekov’s gun in Doctor Who season 15. They are mentioned so frequently by the character but haven’t been shown onscreen or named, which feels like a very intentional choice.

As such, two prominent theories have come up, one of which connects to the Susan cameo. Firstly, some individuals think they don’t exist. Alternatively, other Whovians have speculated that one or both of her parents are someone important to Doctor Who lore. The possibility that Susan could be Belinda Chandra’s mother has become a subject of discussion since the cameo. This would give Belinda an interesting connection to the Doctor. Additionally, the Doctor getting Belinda home would then provide two welcome reunions – Belinda with her parents and the Doctor with Susan.

3 Susan Could Return As A Data Ghost

Susan Might Not Be Alive In The Strictest Sense Of The Term

When I saw Susan in the TARDIS in Doctor Who season 15, episode 6, my mind immediately went to River Song’s death. After she dies, she becomes a data ghost in the TARDIS. Then, she is able to appear as a ghostly projection in “The Name of the Doctor.” With that in mind, my theory is that Susan might have died, and her consciousness is still alive in some way, such as a data ghost. Since decades have gone by, there’s no guarantee that she’s still alive.

If she’s a data ghost, she could appear to the Doctor as a vision. It could explain why she wants them to find her; Susan might hope to stay as a data ghost in the TARDIS with the Doctor. Mind you, this would raise questions such as, “How did Susan die?” “Who helped her become a data ghost?” and “Where is she now?” Realistically, they will need to fill in the blanks about Susan’s life no matter which direction they go, though. While it might not be the most probable answer, Susan returning in this way would certainly be interesting.

2 Susan Will Return As Ruby Sunday's Biological Grandmother

Susan Could Have A Connection To The Fifteenth Doctor's First Companion

Many Whovians still haven’t given up on the idea that Ruby Sunday’s lineage has significance to the Doctor Who lore. People feel spurned by Doctor Who season 14’s reveal, and they have a good reason for that. The Ruby Sunday biological mother reveal was underwhelming, but they still haven't revealed her father or any of her grandparents. Since it seems that Susan will return to the show, Doctor Who could reveal Susan and David as Ruby Sunday’s grandparents.

After all, Ruby will play a role in the two-part finale of Doctor Who season 15. Ruby having Gallifreyan and Time Lord DNA would explain peculiarities about her that still haven't been answered, and it would give Susan a happy ending. At least the Doctor leaving her would be worth it if she found happiness. Ultimately, as enjoyable as it would be for Ruby Sunday to have a connection to Doctor Who lore, it seems unlikely that RTD would backtrack on the “anyone can be special” message at this point.

1 Susan Is Alive Because Gallifrey Survived (Again)

Gallifrey Unexpectedly Surviving Might As Well Be A Doctor Who Meme At This Point

The final entertaining theory about Susan’s return in Doctor Who is that she’s alive because Gallifrey somehow survived the Master’s attack. It’s unknown whether Susan stayed on Earth after the Doctor left or if she somehow went back to Gallifrey. (The Big Finish audio stories answer the question, but they’re unfortunately not part of the Doctor Who show’s canon.) Either way, if Gallifrey wasn’t destroyed, then the Time Lords probably survived.

Anyone who has watched Doctor Who for a while knows that the show likes to destroy Gallifrey and then retcon the decision. RTD revealing the planet as alive would be underwhelming, given the number of times that it has happened. However, it would explain why Susan wasn’t destroyed with the rest of the Gallifreyans and Time Lords. Gallifrey’s survival might also change the Doctor’s mentality about being an orphan with no home in Doctor Who. It wouldn’t necessarily change that they are the Timeless Child, but it would mean that they still have their family.

Out of respect for myself and other Doctor Who fans who have avoided the leaks, please keep the comments section free of any spoilers for the final two episodes.