Spoilers follow! They start out pretty mild but then get very explicit, so read at your own risk, especially past the spoiler warning image. Tread lightly!

In “The Sincerest Form of Flattery,” the standout episode of the recently wrapped first season of Starz’s wonderful new spy drama Counterpart, a young girl learns that she is to have her legs broken.

She’s informed of this, clinically, coolly, by a woman she trusts, the head of the orphanage where she lives. Both of her parents died in a mysterious flu epidemic, and, the woman explains, the girl is part of a long, long process to pay back those believed to have unleashed the flu on the world. It will be painful, but breaking her legs is all part of this plan.

See, Counterpart takes place in our world, but also another, which split off from it in the late 1980s. The two began as exact copies of each other, but in the intervening decades, differences have begun to pop up — first small ones, then greater and greater. The largest was the flu of 1996, which killed 7 percent of the other world’s population and didn’t arise in ours. The two worlds are kept secret from those who live within them, except for various operatives who play in the gray areas in between.

The little girl has to have her legs broken because the other her (on our side) has broken her legs, and when the time comes for the little girl to take her counterpart’s place, she will need to have the same evidence of bone fractures that healed, just in case anyone gets suspicious. Everything she does is meant to perfectly match the other her, in our world. She is unable to live her own life, instead ending up a vague copy of herself.

Is the little girl in training herself, then? Or is she some other version of herself, foisted upon her by a system she was born into as a child and barely understands?

Counterpart is a lot of things — spy drama, Cold War allegory, involving story of a number of marriages in crisis — but it is, above all else, a story about the existential horror that comes from truly getting to know oneself. After all, the version of the girl from our world only comes to know her double when said double murders her, a suicide-homicide that might as well be Counterpart in a nutshell.

Counterpart uses dramatic mirrors and foils in interesting and refreshing ways

It’s not uncommon for a dramatic work to create characters who serve as “foils” to the protagonist, or mirrors of the protagonist. These are characters often designed to needle the protagonist where they struggle, or to reflect back the things they do or don’t like about themselves. (A classic example is Hank on Breaking Bad — he’s everything Walter White is not, and he’s a lawman whom criminal Walt doesn’t want catching on to his enterprise.) What makes Counterpart unusual is that essentially every foil or mirror on the show is some other version of the exact same character.

This is most notable when it comes to the protagonist, Howard Silk, a low-level intelligence analyst who learns, abruptly, that there is another world when the much more ruthless and cutthroat Howard (who’s a much higher-level spy, naturally) comes over to our side and requests a meeting. Both Howards are played by J.K. Simmons, one of our best actors, and it’s remarkable how easily he indicates which Howard you’re watching via an arched eyebrow or a simple shift in posture. (Here I should indicate that “our world” is known as Alpha and the “other world” as Prime. Hence, our Howard is “Howard Alpha.” This will hopefully keep things clear.)

But creator Justin Marks and his team aren’t interested in presenting the Howards as opposites of each other. Instead, Counterpart wants to explore how both Howards have always had elements of the other within them.

Howard Alpha and his wife, Emily (Alpha), were about to have a baby when she miscarried. But Emily Prime didn’t miscarry, and the couple’s daughter, Anna (Sarah Bolger), now hates Howard Prime for how little involved he was in her life and for divorcing her mother. (Both Emilys are played by Olivia Williams.) Did the miscarriage and resulting fallout cause Howard Alpha to become more compassionate in some ways? Would he, too, have become a disconnected, uninterested father? Or did larger events beyond both men push them inexorably away from each other?

This question moves to the forefront as the two Howards assume each other’s lives on either side of the divide between worlds, as Howard Prime attempts to figure out who’s ordering the assassinations of important operatives in Alpha World. Howard Alpha is just supposed to hang tight and do his best Howard Prime impression, but he’s quickly getting drawn into a major investigation alongside Emily Prime (whose Alpha version is in a coma after a mysterious accident shortly before the series begins), relishing the chance to spend time alongside some version of his wife. He also bonds with the daughter he never got a chance to have.

What sets Counterpart apart, however, is the ways in which it quickly grows beyond its protagonist(s) to be about an entire world. It’s a feat of world building, sure, but mostly because we see the two sides of the divide through the eyes of a variety of complicated characters, most of whom have other selves designed to get viewers to ask questions about the nature of identity and the self.

These dramatic foils, then, aren’t just a fun way to create a spy series where you can never be quite sure of anybody’s allegiance — or even their true identity. They’re a way to ask fundamental questions about the person you see when you look in the mirror.

Counterpart is about nature versus nurture — except it assumes that question is true throughout your life

We’re seeing a surprising surplus of compelling spy dramas on the air right now, from longtime stalwarts like Homeland and The Americans to BBC America’s twisty new series Killing Eve and Counterpart. I suspect this is because we live in a world where the Other has become easy to demonize, and spy fiction is always about the uncomfortable nature of realizing how much the Other is just like you, even as you try to stop them.

On Counterpart, stopping the Other often means trying to stop your exact opposite, trying to anticipate the actions that you yourself might take under different circumstances and maybe realizing how little you know yourself, really. When Clare (the woman trained as a young child to take over for her Alpha self, played by Nazanin Boniadi) kills her Alpha self, does she really see that self as an extension of her? Or as a target? Do any of us really see ourselves?

Weirdly, the psychological condition Counterpart most makes me think about is body dysmorphia — the idea that you have a vastly distorted idea of what you actually look like, so looking in the mirror to reveal the truth provides a brief shock at best and genuine mental trauma at worst. All these characters think they know who they are, until different versions of themselves step out of the mirror and inform them they have no idea.

It would be tempting to boil down the series to a “nature versus nurture” debate, especially in the case of Clare. Clare Alpha was raised by loving parents; Clare Prime was raised by a secret school that aimed to make her a deadly spy. But what turns Counterpart into more than a fascinating fictional experiment is the way it decides nature versus nurture is a debate that continues inside of us right up until the moment of our deaths.

You can still change. If everybody starts believing that Howard Alpha is Howard Prime, then he will start to become more like Howard Prime. But there is also something about him that is innate, that can repair the relationship with the daughter that is genetically his but that he literally never had. Marks has talked about this in interviews as finding the “true” Howard — locating where Howard genuinely lives on the sliding scale between Alpha and Prime. But I think that’s only half of the picture. We all have masks we wear in different situations. By meeting their other selves, both Howards find new masks to wear when they need to.

All of the above makes what’s ultimately a very entertaining spy show, with perfectly paced reveals and a dexterity with a stripped-down action sequence (to say nothing of beautiful visuals that reduce Berlin to a game board of lines and angles), sound like a chore, a psychological treatise masquerading as a TV show. But the beauty of Counterpart is right there in its protagonists. Sometimes, it’s possible to be both.

Counterpart’s first season is available to stream in its entirety on the Starz streaming app.