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Doctor Who: Who is Ruby Sunday? Top theories, hints and more

Millie Gibson plays the Doctor’s new companion

Emmy Griffiths
TV & Film Editor
May 28, 2024
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Doctor Who’s rebooted series starring Ncuti Gatwa and Millie Gibson has just aired what critics have called the best episode of the sci-fi show in years - and the story was centred around the Doctor’s new companion, Ruby Sunday. 

Ruby, who is played by Millie in the hit show, finds herself in a nightmare when she visits Wales with the Doctor only for him to disappear after stepping into a fairy circle - and for a woman to appear in the distance making various hand gestures. Despite trying to communicate, Ruby works out that the woman stays 73 yards away from her at all times, and - it’s a long story - but she eventually uses her new stalker to prevent a nuclear war. 

Ruby and the Doctor became instant best friends on the show© James Pardon
Ruby and the Doctor became instant best friends on the show

As we follow Ruby growing up, the final minutes of the episode reveal that she has been the woman following herself all of her life. Then the scene changes and Ruby is the young version of herself again, having forgotten her entire lifespan - but this time she stops the Doctor from stepping inside the circle, appearing to correct the timeline. 

Ruby is followed by an old woman© James Pardon
Ruby is followed by an old woman

The episode, as well as several tidbits from Ruby’s storyline including the mystery of her parentage, as she was left abandoned at a church on Christmas Eve, her ability to make snow occur wherever she goes, her ‘hidden song’ that Maestro uncovers, and the machines in Boom’s inability to work out her origins are all reasons behind why fans know that there is much more to Ruby than what meets the eye. 

Ruby still doesn't discover her parentage in Boom© James Pardon
Ruby still doesn't discover her parentage in Boom

The showrunner Russell T Davies has confirmed that fans will get answers this season, saying: “I mean, there is a meaning, there is a significance, it will be explained. It's not going to be one of those annoying mysteries that at the end of the season, we go, ‘Ahh, keep watching. We will continue this mystery.’ There's a definite answer. It is meant to be a mystery.”

What are the top theories about Ruby? 

There have been many, many theories about who Ruby Sunday really is, but here are just a few of our favourites. 

Things get very creepy in 73 Yards© James Pardon
Things get very creepy in 73 Yards

Ruby is a Time Lord

The Doctor’s perception filter works on humans, who see the TARDIS but don’t pay any attention to it, and Kate Lethbridge-Stewart tells Ruby that the same applies to the woman following her in 73 Yards. With a perception filter, no one except Ruby notices her - and the filter also doesn’t work on Time Lords. Since Ruby’s origins are totally unknown, could she be from the Doctor’s home planet? 

Who are Ruby's parents?!© James Pardon
Who are Ruby's parents?!

Ruby is a Timeless Child 

There is a distinct link between the Doctor and Ruby as they are both Foundlings, and both don’t know their origins. Ruby doesn’t share any DNA with anyone on any database, and both the TARDIS and the futuristic machines in Boom fail to identify who she really is. She also has a knack for finding other foundlings, including the children in Space Babies - could the connection be that she is one of the original foundlings herself? 

She has a mysterious knack of finding Foundlings© James Pardon
She has a mysterious knack of finding Foundlings

Ruby is the child of ‘the One Who Waits’ 

There have been many hints about another unearthly entity who will be one of the big villains of the season, with Maestro and the Toymaker alluding to the terrifying enemy. In The Devil’s Chord, Maestro appears to realise that ‘The One Who Waits’ was there on the day of Ruby’s birth, but doesn’t understand why. Neither do we, Maestro! 

Ruby is found to have a 'hidden song' in The Devil's Chord© James Pardon
Ruby is found to have a 'hidden song' in The Devil's Chord

Ruby is a work of fiction 

After Wild Blue Yonder, the Doctor worries that he incited a suspicion (about binding in salt) at the edge of the universe, and the impact that will have in time and space. It has been evident throughout the season that the show has taken on a much more ‘supernatural’ element, with Ruby’s experience in 73 Yards being something taken straight out of a ghost story. 

Ruby’s lack of origins as well as the introduction of supernatural beings like the goblins, fairy circles causing the Doctor to vanish, and the children creating the ‘bogeyman’ on a spaceship all hint to there being a link between fiction and reality - so could Ruby be linked to it all? 

Ncuti Gatwa as The Doctor© James Pardon
Ncuti Gatwa as The Doctor

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