"Shut Up and Dance" is a particularly harrowing episode of the new season of Black Mirror—if only because it's built around every teenager's worst nightmare. After retreating to his bedroom for some private time with his computer (hint: he grabs a box of tissues on the way), Kenny (Alex Lawther) gets a message from an unknown number—"WE SAW WHAT YOU DID"—along with a video of the deed, shot directly from his hacked webcam. The hacker offers Kenny a bargain: Complete a series of bizarre tasks, and the video will remain private. Fail, and the video will be sent to every single person in his contact list.

"Shut Up and Dance" is particularly unnerving because it feels so plausible; unlike more far-out Black Mirror episodes like "15 Million Merits" or "White Bear," it takes place in a world that's basically identical to our own. And with cameras on pretty much every device we own, it's horrifying to think about the private moments that a malicious hacker might capture. (True confession: Before I had even finished watching the episode, I made like Zuckerberg, grabbed a Post-It note, and covered up the built-in webcam on my laptop.)

What's it like to be at the center of a story that grapples with the way technology has impacted our collective sense of security and privacy? I talked to "Shut Up and Dance" star Alex Lawther—an acclaimed up-and-comer best known for playing the young Alan Turing in the Oscar-nominated biopic The Imitation Game—about anchoring one of Black Mirror's most nightmarish fables.

I'm glad we're speaking on Black Mirror's release day, because I can only imagine how hard it's been for you to discuss this episode without spoiling any of its secrets.

Yeah! It's lovely that we can finally talk a bit more freely about this. So many Black Mirror episodes hang on the conceit or the twist, so it's a joy to finally be able to share it.

Were you already a Black Mirror fan when you auditioned for the lead role in "Shut Up and Dance"?

Yes. I was a huge fan. [laughs] I particularly liked "White Bear," in which a girl is followed around by people filming her the whole time, and you don’t learn until the end what has led her to end up in such a situation. And then there's the classic—the prime minister and the pig. The very first episode. They're all such wonderful standalone movies, in a similar sort of universe. Very dark. You could just watch one and mull over it for a month. But I sort of had to put all that to one side of my mind, and consider ["Shut Up and Dance"] for what it was on paper. Even if I had never seen Black Mirror before, or heard of it, the script alone was enough to get excited. When you get a script like that… they come rarely. So it was doubly a privilege. To be a part of that, and to be a part of the cult that is Black Mirror.

What it's like to get involved with a project as notoriously secretive as Black Mirror? Did you know what you were getting into?

At first, I auditioned with only a couple of scenes. It was very top-secret. As I got further in the audition process, they released the script—but even in the preliminary scenes I read, I was very excited by the premise. I knew there was a boy called Kenny, trying to deliver a cake to somebody. And he seemed very worried. [laughs] But I didn't know exactly why. That was all I had to go by. I had no idea about the twist that comes at the end.