Steven Moffat Talks Introducing [Spoiler] & What Wasn’t in First Draft of ‘Boom’ Script

[Warning: The below contains MAJOR spoilers for Doctor Who Season 1 Episode 3 “Boom.”]

Welcome back to Doctor Who, Steven Moffat! The former showrunner wrote the latest episode, which puts the Doctor (Ncuti Gatwa) and Ruby (Millie Gibson) in the middle of a battlefield, with a few twists along the way. The one that will have everyone buzzing first is obviously the casting for one of the Anglican Marines (just one of several nods to Moffat’s Doctor Who past): Varada Sethu—who’s joining the series in Season 2 as a new companion—as Mundy.

Moffat, understandably, is mum when it comes to even hinting at what’s ahead for Sethu on Doctor Who. “[Showrunner] Russell [T Davies] has a plan, and I don’t know what the exact details of his release of that plan are going to be,” he tells TV Insider. “I simply wrote the character of Mundy, and she did what she had to do in the story.” Will she even be playing Mundy in Season 2? We’ll have to wait and see.

But looking at her interactions with the Doctor and Ruby in this episode (ahead of Sethu starring alongside Gatwa and Gibson), “it was quite important that she be a formidable and kindly person,” explains Moffat. “She’s very, very tough and she’s notionally the Doctor’s enemy, but in the end, she wins the Doctor’s respect because she stands by what she believes in—and she shoots him three times in the arm, which is never very friendly, but she wins his respect.”

He continues, “I’m always cautious when you’re doing things like—the Doctor is quite intemperate when it comes to soldiers, and he’s quite intemperate when it comes to religion, but he has a grudging respect for both. He’s a scientist adventurer. Of course, he does have those slight disdains, but he frequently discovers there’s more to those people than he initially assumes, and there’s more to Mundy than he initially assumes. She’s tougher and stronger. He doesn’t always enjoy that, but you can’t really enjoy someone’s obstinacy when you’re standing on a landmine.”

That landmine is part of the security system in place for a war that’s not actually being fought; the Anglican Marines thought they were in the middle of battle, with the “Ambulance” (another character played by Susan Twist) evaluating the injured. In some cases, death was cheaper than recovery time (as is true for one soldier whose eyesight wouldn’t be fully recovered for four weeks).

Moffat did ask “all the appropriate questions” and “got all the answers to what I needed to know” about the mystery of Twist’s characters. “You’ll find out as the story unfolds,” he says. “I do know the answer.” In fact, originally, the Ambulance didn’t even have that face!

“It’s always good [to have a face],” he says. “It also gives you something to be deceptive about. What is that big floaty face? What’s going on? It wasn’t in the first draft as a face, but I did it later on.”

“Boom” explores the complexity of AI with the Ambulance but also the humanity of the situation, with an approximate reconstructed version of a soldier who ends up helping the Doctor. “It is just a chilling idea,” according to Moffat, “the idea of the battlefield, shell shocked soldiers being sent back to the front. I understand it. I don’t know what else you could do, but it’s always chilled me. That’s what we do. We patch ’em up and send them out to get shot at again. In this case, it’s even more brutal. You’re too expensive to keep alive. It’s not fair, this judgment, but there is something mad about a hospital service in a field of conflict where you’re deliberately injuring people. You could stop. But obviously life is a little more complicated than that.”

The Doctor, moments after he and Ruby first arrive on the planet, steps on a landmine, where he remains for most of the episode. Moffat gives Gatwa great stuff to play with while he’s stuck in that one position.

“I’d seen the audition. It was very early on. This was ages ago. I was involved right at the start. I’d just been lying through my teeth,” Moffat admits with a laugh. “He’s such a lively, bouncy Doctor who runs all the time, like he’s so in love with life he can’t stop dancing, so to make him stop dancing and stand still is immediately arresting, right? If you’re writing a Sherlock Holmes story, you want Sherlock Holmes to look confused because he never is. If the Doctor runs and dances, you want him to stand still and look frightened, just not all the time, but to show another side, to show another part of him.”

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The episode also throws quite a lot at Ruby: It’s her first time on an alien planet, but she doesn’t really have time to stop and marvel at it because of the danger around them. In fact, she insists on stepping right into the danger zone to give the Doctor a canister to use to counterbalance his weight so he can put his other foot down and she ends up, in her attempt to help him later on, getting shot and nearly dying. (The snow from the night she was left at the church once again comes through, this time freezing, and she gets stuck on the question of her next of kin because she doesn’t know who that is, with her birth parents’ identities a mystery.) And remember: Ruby is young.

“The Doctor chooses with great care—sort of—and also, equally relevantly, the companions choose the Doctor, maybe actually more relevantly,” Moffat notes. “Nobody would go through those blue doors who wasn’t a thrill seeking adventurer. He’s clearly mad, and he’s still living a mad life. I would run amok in reality, if the Doctor invited me on the TARDIS. You say you’d go, but I always know when he says, ‘I’ll show you the wonders of the universe,’ that the wonders of the universe will be an underground tunnel full of psychopathic robots. This is the truth about traveling with the Doctor.”

He continues, “She is young, and it’s madly irresponsible what he does. Everyone’s young to him, but at the same time, it’s incredibly thrilling. He might be your best friend, but he’s also your most dangerous friend. And she’s great, and she earns her stripes in a way this time. She insists on handing the cylinder to him. That’s the kind of person who’d go on board the TARDIS. You know every time you run out those doors, you might not come back.”

Ruby handing the Doctor the cylinder was “a great scene to write,” for Moffat. “The Doctor has lost his ability to do anything at all. Quite a lot of what the Doctor does is dancing around and distracting people with his screwdriver. He has to stand still, there’s nothing he can do about it. She just keeps walking towards him, and it’s the first time she’s seen him like that in a way. So it was a good scene to write it, and I think they played it beautifully. And also he’s so afraid in it.”

As the Doctor and Ruby leave at the end, he tells Mundy he’ll be popping in every now and then, and fish fingers and custard are his favorite, a clear nod to the Eleventh Doctor (Matt Smith). Moffat was showrunner then and wrote Season 5‘s “The Eleventh Hour,” during which the Doctor discovered his love for the food. “Paying tribute to myself, it’s rather odious really, isn’t it?” he laughs. “It’s 14 years ago. I hadn’t realized that. Suddenly I thought, ‘My God, that’s 14 years ago.’ That’s a very old episode. I was young.”

Disney+ / BBC

There are quite a few references to his run throughout this episode. “I’m afraid I should have controlled it better than that, frankly, but I do like making a few back references,” he says. “But I’m always very careful about it because if you’ve never seen the show, they still work. I mean, just the fact that he likes fish fingers and custard is fine. If one day you’ve become so enthralled by Doctor Who you go and check the old ones, you’ll see, yep, he really does. He actually eats it, but you’re careful with that. It’s like the Bond movies, throwing in sly little references that won’t get in the way of anyone watching it. But the people who love it better know that they’ve had a special little nod.”

Moffat has written another episode for this run of Doctor Who: the 2024 Christmas special, which includes Bridgerton star Nicola Coughlan. He won’t say anything about the episode itself other than it’s Christmas. “I couldn’t turn that down because I love doing the Christmas ones. I absolutely love Doctor Who on Christmas Day, and I had thought, ‘Well, I’ve done ‘Boom,’ I don’t need to do another one.’ Then Russell emailed me and said, ‘Do you want to do Christmas? And I said, ‘Oh, well, right. Got to do that.’”

It’s the 50th Doctor Who episode he’s written… sort of. “I had no idea it was my 50th, and I still don’t think it really is, because that includes my co-writes,” he says. “Technically, I think it’s my 44th. There are a few other ones I’ve co-written, and there’s loads more that I actually fully rewrote and never took a credit for. So it’s all a bit foggy. But in terms of straightforward single credit, Doctor Who, that is my 44th.”

So that means we need six more from him to get to that 50th. “Do we need that?” he asks with a laugh.

What did you think of the latest episode and Sethu’s introduction? Do you think she’ll be playing the same character in Season 2? What are your theories about her, Susan Twist’s characters, and everything Ruby Sunday? Let us know in the comments section, below.

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