Well, it’s time for the Seventh Doctor to do like all Doctors before him have done and face off against one of the Doctor’s oldest foes.
See, every 25 years, a meteor comes close to Earth. There’s a silver statue of some kind inside it. On Earth is a bow made of the same metal and an arrow to go with it. The Doctor knows that putting all three together will lead to nothing but destruction, but he had to remember that was what he set his pocket watch for. Ace, meanwhile, is along for the ride which includes taking the TARDIS to Windsor Castle and seeing the Queen (implied since the show wasn’t given permission to film at Windsor and the Queen is a look-alike seen from a distance that has no lines or a clear look at her face).
See, the meteor comes down nearby, and the Doctor knows that people will be after it. In particular, he sees three factions after it.
One is a 17th century time-traveling sorceress, Lady Pienforte. She has a servant/sidekick and the arrow. The Doctor apparently messed with her before. And yeah, he says she uses magic so I guess magic is real now.
Another faction is a group of Neo-Nazis from South America. They have the bow and want to use the power of the statue to form a Fourth Reich. Lousy Nazis…
And then there’s the third faction, one whose timely arrival may have saved Ace from a Nazi firing squad at the meteor.
But the third group are the Cybermen.
So, yeah, this could get ugly. Nazis and Cybermen at the same time…