Well, it seems there is a reason for the Doctor to have a job at a university. He’s supposed to stay put unless there’s an emergency.
Has anyone ever considered the Doctor is not the type to stay put anywhere?
Yeah, it seems the Doctor took a vow to guard a certain vault underneath the university with Nardole, and unless something big comes up, he’s not supposed to go anywhere. Naturally, the first chance he gets, he opts to take Bill anywhere she wants to go. She opts for the future, leaving Nardole behind suspicious but theoretically none-the-wiser.
Well, that takes Bill and the Doctor to a colony planet where had they seen the cold open, they would have seen these weird robots with smiley faceplate faces helping swarms of things kill all the humans. The Doctor doesn’t really know that, but he and Bill are given these buttons that register their moods, but are visible only to other people. Oh, and the robots, and they seem to communicate entirely with emojis as avatars to the nanites the Doctor calls the Vardy that make up most of the empty colony.
Bill, for what it is worth, asks smart questions. Why doesn’t the TARDIS have seats next to the control panel? Where’s the steering wheel? Why didn’t the Doctor mention having two hearts? She’s a bright young woman, and her general excitement to see everything actually helps because it turns out the Vardy are killing anyone who gets upset. So, as the Doctor explains that a colony like this would send an advance team ahead to prep the place, the rest of the colonists would come along later. Sure, the Doctor finds a locket in a pile of dust and then they find a bunch of human bones, but…
But getting out is easy if you just use some fake smiles.
So, what now? The Doctor wants to find the source, namely the ship the robots and dead people came in, and use it to shut down the robots.
Not a bad plan. Bill follows even though she isn’t supposed to, but a good companion tends to do that anyway. Plus, the Doctor finds creative ways to keep her busy when he doesn’t really need her help, but there is this big empty space inside the ship that…oh, wait, there’s the problem. The Doctor can’t shut the robots down because the rest of the colonists are inside the ship and they might be the last of the human race. Bill also found an old woman who had died.
And that solves everything. Apparently, the Vardy were programmed to make people happy by setting up a comfortable place to live, but at some point, they evolved further to define an enemy of happiness as anyone who wasn’t happy, and when someone died of natural causes and made people grieve…the Vardy decided they had to go.
Oh, and some kid just wandered outside, not knowing his mother is a fine powder.
This will get bad.
But the Doctor is there, and he basically realizes the Vardy are now a sentient lifeform, and robots can be rebooted. The humans will probably need to negotiate with the Vardy on a tenet/landlord sort of basis, and everything will be fine. He can even take Bill back in the TARDIS to the exact time they left and Nardole won’t be the slightest bit suspicious.
You know, until they find an elephant standing on the frozen Thames. I think they went somewhere else by mistake again.