Now four episodes into the latest season of Doctor Who, it is so far turning out to arguably be Peter Capaldi’s best season as the Doctor. That said, all good things must come to an end. With the weeks creeping by, the hour of his inevitable death and regeneration is drawing near and Whovians are grasping at any hint of a rumor they can in deciphering the when and the where of Capaldi’s final scene. Fans of the long-running science fiction series may have figured out the answer to the question that has been teasing audiences ever since the beginning of the season, which may be related to this version of the Doctor’s demise – who (or what) is inside the vault underneath the school? It appears that the BBC have thrown us a bone during the show’s latest episode ‘Knock Knock’.

At the end of the episode, we see the Doctor take Nardole’s place watching over the vault. He has also brought Mexican food to share with the presumably humanoid prisoner within the vault. During the scene, a rendition of ‘Fur Elise’ is played on a piano coming from within. After he promises to tell the prisoner a tale about children being eaten, the tune switches over to ‘Pop Goes the Weasel’ which suggests that whoever his prisoner is has a rather distasteful sense of humor. According to several Whovians on Twitter, the clues add up to suggest that fan favorite Missy is inside the vault.

We've seen what's in the vault. It was in the trailer! It's Missy. In a cage. Sitting on that piano? 🎹 Still excited to see her. #DoctorWho pic.twitter.com/2zYlUMjv7u

— Séan 👾 (@SeanEdits) May 6, 2017

As mentioned above, Missy was actually seen in one of the trailers for this season of Doctor Who, laying atop what appears to be a piano. Pair that with what occurs at the end of ‘Knock Knock’ and we have ourselves a locked up Time Lord (or lady, in this case) with a sick sense of humor and a penchant for the macabre played by Michelle Gomez. Only time will tell if the fan theory is correct, though chances are rather high that Missy will be making her grand debut this season from within the confines of the vault.

So, what are your thoughts on the Doctor Who fan theory? Do you think someone or something else is in the vault? Let us know in the comments section below and, as always, stay tuned to DFTG for all the latest gaming and entertainment news! Don’t forget to follow us on Twitter for our 24/7 news feed!