But unlike that episode, where a woman revived her dead boyfriend by using his social-media history to rebuild his personality inside a synthetic clone, “San Junipero” isn’t a sad ballad of well-meaning tech gone wrong. It’s the story of a different kind of world, one we might eventually arrive at, that will have its own flaws and limits as well as a uniquely powerful purpose. There are a lot of ways Brooker could have approached writing this episode, but his smartest move was to focus on the budding romance between Yorkie (Mackenzie Davis) and Kelly (Gugu Mbatha-Raw) while slowly, but surely, building out the mysterious world of San Junipero around them.

Yorkie is mousy and shy, clad in khaki shorts so dorky they almost loop around to being cool (almost). She goes to San Junipero’s loud, bustling nightclub but mostly hangs out by the arcades, rebuffing any attention, until she meets the very extroverted, very cool, very ‘80s Kelly. There are strange, unexplained touches in the first half of “San Junipero”; Yorkie seems able to quickly change her hairstyle and clothes dramatically when deciding what to go out in (she always settles on those khaki shorts). Kelly always has her eye on the clock, waiting nervously for the midnight hour to strike. And then, when Yorkie searches for Kelly again after they sleep together for the first time, she somehow jumps through different time periods, each marked with appropriate historical and fashion details, to see where she’s gone.

That’s because San Junipero is a virtual world, a massive database in the cloud that people’s consciousness can be uploaded to, guaranteeing virtual immortality to the dead (who make up 80 percent of the population). Yorkie and Kelly are both tourists, allowed only to visit for a few hours every week. In the real world, Yorkie is a paralyzed gay woman who never got to live a real life because of intolerant parents and a tragic accident. Kelly, on the other hand, is an older woman who recently lost her husband; he refused to enter San Junipero, finding the entire concept of virtually cheating death fundamentally inhuman.

It may sound grim, but this a surprisingly upbeat tale, one that doesn’t make an easy judgment about what any of the characters decide to do with their lives and their afterlives. Yorkie is of course thrilled to enter San Junipero and embark on a new life with Kelly; Kelly is more cautious, worrying that the virtual immortality it grants will eventually hollow out her soul as she endlessly searches for new experiences. It’s the strange paradox of the copy-pasted brain, one that a lot of science-fiction has explored recently (like the wonderful film World of Tomorrow and the terrific video game Soma).

What makes “San Junipero” work, and what makes Yorkie and Kelly’s eventual decision to be together so effective, is its performances. Davis and Mbatha-Raw have such instant, lived-in chemistry, and convey a whole lifetime of angst and desires in just a few interactions. This is the only Black Mirror episode this season that really earns its running time, I think, because it really covers a grand emotional arc in these 60 minutes, rather than padding for time. Did you find “San Junipero” as moving as I, Sophie? And does Belinda Carlisle’s “Heaven is a Place on Earth” now have new meaning for you?

Read Sophie Gilbert’s review of the next episode, “Men Against Fire.”

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