Bill may have chosen to go the future last week, but as this week’s episode shows, the TARDIS ensured that our newest companion gets to experience the past as well, taking both the Doctor and her to 1814 London. Honestly, I wouldn’t be surprised if Idris is just as fond of Bill as we are. And given Bill’s admission that she’s “lowkey in love” with the TARDIS’ penchant for trouble and possession of dresses, it’s clear the feeling is mutual — which of course makes me hope they might eventually get to meet. But alas, seeing as how Bill might just be a companion for a season, this could be a story relegated to the realm of fanfiction.
In any case, turns out Regency Era London is not only home to Jane Austen’s brand of social comedy, but also a ginormous creature — which the Doctor aptly nicknames “Tiny,” the “Loch-Less Monster,” and “the Not-So-Little Mermaid” — that lives under the frozen Thames, allowing it to remain frozen and house the current ice fair.
After they witness one of the street urchins who tried to steal the Doctor’s sonic screwdriver become the creature’s latest meal, the Doctor and Bill venture underwater in old-timey diving suits to suss out the situation. Turns out, it’s not the creature’s fault — people are being fed to it by some bioluminescent alien-ish angler fish. It’s chained and in pain, presumably having been kept this way for years. The sight is haunting both to Bill and the viewer.
This new discovery prompts Bill and the Doctor to visit the men dredging up the river for the creature’s droppings, which apparently make some kind of fuel that burns not only longer and hotter than coal but also underwater. This leads them to theorize that Lord Sutcliffe, who’s in charge of the whole operation, is an alien. After all, how else would someone display this much lack of compassion?
But as they realize upon meeting the man, he’s a 100 percent human, and a 1,000 percent scumbag. Not only has his family known about the chained up creature for decades, but he’s perfectly fine sacrificing people to it. In fact, he’s got a plan to blow up the Thames later so that people assume it’s a fireworks accident and forget about the disappearances and move on — only now, Doctor Disco and Bill are also going to be two of the lives lost as they’re tied up in a tent on the ice. Like I said, scumbag.
Thankfully, the Time Lord and his companion quickly manage to fish out the sonic screwdriver. But before he can really free them, the Man With the Ship Tattoo arrives and confiscates it. Unfortunately, he missed the Doctor’s whole explanation about how the anglerfish are attracted to sound, which is how they know when someone is by themselves, and perfect for the taking. Just before he falls through the ice, Tattoo Man tosses the Doctor the sonic screwdriver.
Now free, Bill recruits the street kids to help clear the ice. Sutcliffe tries to stop people from fleeing the soon-to-explode river, but when that doesn’t work, he moves up the timeline of his explosion. Only when he does set it off, it doesn’t work like he planned. As we then learn, the Doctor was able to use his diving suit (which was somehow nearby?) and place all the explosives by the chains trapping the fish. Not only does this cause the ice to crack, it also sees Sutcliffe plummet to his death under it. With that, Tiny swims off to freedom, with Bill grinning at how happy she sounds.
As for the kids? With Sutcliffe gone, they “Doctor” his papers saying that Perry, the young boy of the group, is his long-lost heir. (Because apparently, girls aren’t eligible. But I suppose, one social issue at a time.) When the Doctor and Bill arrive in the present — just as Nardole is bringing them their “coffee”-flavored tea — they check on the past to see that their handiwork stuck. The Doctor credits this to Bill, whose “order” it was to do so.