The vault is still not open, and there is something much more frightening than Missy to contend with.
Of course, this week’s big cliffhanger left us with The Doctor telling Missy exactly what he shouldn’t have, letting her know he’s blind and that he’s going to need her help.
As “Extremis” had revealed, there’s a parallel universe that has been operating as a testing ground for an alien race that’s looking to invade our world.
So naturally, with the mystery of the vault solved, the new question of the hour seems to be, what’s the new coming darkness that The Doctor seems so mortified about at the end of this week’s episode?