Caution: spoilers ahead for Doctor Who season 15's "The Well."

After all the Doctor's many adventures in Doctor Who season 15's "The Well" is revealed to be a sequel to season 4's "Midnight," in which a solo Tenth Doctor found himself among the engers of a broken-down shuttle being assaulted by a mysterious presence. In another shocking turn of events, Ncuti Gatwa's Fifteenth Doctor blankly describes the experience with a choking ission: "I have never been more scared in my life."

Not to detract from the peril of "Midnight," but it feels like the Doctor's past regenerations should have hundreds of more frightening memories than the one from Doctor Who season 4. The War Doctor endured numerous harrowing tragedies as a consequence of the Time War. The Fifth Doctor watched one companion die, then sacrificed himself to save another. The Twelfth Doctor spent an eternity fighting his way back to Gallifrey, and Thirteen had her entire existence turned upside down. To call "Midnight" scarier than the above seems like an exaggeration at first glance, but it actually makes perfect sense.

The "Midnight" Monster Took Away The Doctor's Voice & Made Him Helpless

"Midnight" Left The Doctor Speechless

The scariest part of "Midnight", from the Doctor's perspective, was not being assailed by a faceless entity that had never before been recorded as a life form. It wasn't even being trapped in a confined space with Merlin and Bianca's mother from Eastenders. What truly terrified the Doctor was the monster's ability to steal his voice. After a period of mimicking, learning, and adapting, the monster began controlling the Doctor's speech, entering his mind and talking through the Time Lord's own mouth. The Tenth Doctor was left helpless on the floor of the shuttle, and was only saved by the courage of another enger.

David Tennant's character was visibly shaken by the experience.

While the Doctor has faced bigger threats in Doctor Who's long history - Daleks, wars, Weeping Angels, the gods of the Pantheon, etc. - the hero has always retained a voice to speak out against the evil. Even when the Doctor didn't have a plan, allies, or favorable odds, he always had the ability to fight back with his greatest weapon: words. The Midnight monster changed that, and with remarkably little effort, so while the episode may not be Doctor Who's scariest from an outside point of view, it's certainly hard to think of a time when the Doctor was more vulnerable.

The Fifteenth Doctor's "never been more scared" line perhaps shouldn't come as such a huge surprise. In the final moments of "Midnight," the Doctor cut an uncharacteristically somber figure, even refusing to laugh at one of Donna's trademark attempts to lighten the mood. David Tennant's character was visibly shaken by the experience - a rarity for Doctor Who. As such, Fifteen's big claim in "The Well" makes a lot of sense.

The Doctor's Fear Proves How Dangerous The "Midnight" Monster Really Is

If The Doctor Is This Scared, You Should Be Too

Even after "The Well," very little is known about the monster at the heart of the story. Its appearance, species, power, and origin are left largely ambiguous, and viewers are barely any wiser than they were at the end of "Midnight." Instead, Doctor Who allows the Fifteenth Doctor's fear to convey how strong the monster is.

Seeing the Doctor so distressed, and even calling his last encounter with the monster the scariest time of his life, immediately establishes Midnight's resident spook as a threat on par with the Daleks, Cybermen, Weeping Angels, and the Master. In the absence of baying fangs, powerful lasers, threatening speeches, or grand plans to take over the universe, one look into the Fifteenth Doctor's eyes proves more than enough to clearly spell out why everyone involved in "The Well" finds themselves in immense danger. Doctor Who cleverly allows the monster's reputation to do all the heavy lifting.

The Ending Of "The Well" Sets Up A New Major Villain For The Doctor

A New Doctor Who Villain To Battle Across The Stars?

Curiously, the final moments of Doctor Who's "The Well" confirm the Midnight monster's survival. The unseen phantom has been released from its planet and is now free to roam throughout the galaxy, meaning it will likely resurface in a future Doctor Who episode. The Doctor will, therefore, need to face his greatest fear again before long.

The monster occupied the Doctor's mind in Doctor Who's "Midnight" episode, so knows all there is to know about the universe's savior.

Had the Fifteenth Doctor not described "Midnight" as the most scared he has ever been, "The Well" revealing the monster's survival would have packed a lot less punch. The camera-shy villain would have simply ed the scores of other galactic terrors that have beef with Gallifrey's last Time Lord. Because the Doctor comes across so unsettled and fearful, however, the prospect of this creature roaming from planet to planet sets up a brand-new long-term rival for the Doctor to battle again and again in Doctor Who's future - a danger as unending and personal as the Daleks or Weeping Angels.

The big difference this time, of course, is the Doctor being at a huge disadvantage. The time traveler knows everything there is to know about the Daleks and Cybermen, and knows the Master better than the Master even knows himself. The Weeping Angels, meanwhile, were familiar to the Time Lords before "Blink." By contrast, the monster occupied the Doctor's mind in Doctor Who's "Midnight" episode, so is intimately versed in the universe's savior. For once, the Doctor is less of an "oncoming storm," and more of a sitting duck.