Doctor Who survives off of big mysteries — even the Doctor’s name itself hasn’t been revealed in more than 60 years. While some mysteries, like the crack in time or the constant appearances of Susan Twist, lead to epic season finales, there are smaller questions, like why there aren’t any ducks in a duck pond, that could go unanswered for years.
In the wake of Doctor Who’s freshly rebooted season on Disney+, one theory reveals why Ruby Sunday was denied a key lifeline at a terrifying moment: it’s more than a question of plot convenience, it’s a matter of paradoxes.
In the standout folk horror episode “73 Yards,” the “Doctor-lite” episode mainly follows Ruby Sunday, as she tries to find the Doctor after he suddenly disappears and a woman starts stalking her from a distance. Her first instinct, like many companions, is to retreat back into the TARDIS. But when she tries to open the door, it won’t budge — the TARDIS is actively trying to keep her out.
So why can’t she get in? A theory originally posted by ScreenRant suggests that the TARDIS shut its doors in order to keep Ruby Sunday from tearing the space-time continuum. Doctor Who has a relaxed relationship with time contradictions: within its universe, some moments are fixed, and some are in flux. But by the end of “73 Yards,” we learn that the old woman following Ruby is actually her older self. So if Ruby entered the TARDIS after being scared by her older self, she wouldn’t have been on the path to become her. No matter what the nature of that moment in time was, the temporal loop had to be closed.
But does the TARDIS really have such precise control over who enters its doors? In the 12th Doctor era, Clara Oswald was denied access by the TARDIS multiple times, and a minisode even revealed that the ship hid her bedroom entirely. It’s not just a petty squabble: Clara popped up multiple times in the Doctor’s timeline, earning her the nickname “The Impossible Girl.” She was, essentially, a walking paradox, so naturally the TARDIS was hesitant to accept her.
The TRADIS is definitely one of the main characters of Doctor Who, whose dependancy as a time-and-space machine can best be described as taking the Doctor “not necessarily where they want to go, but very often where they need to be.” Clearly, that knowledge extends to the Doctor’s companions too. Being locked out of the TARDIS may not have been what Ruby wanted at the moment, but it set her on a path to heal history and reunite with the Doctor.