WARNING: Spoilers from the start. Don't read this unless you've watched episode seven of Stranger Things 2.
At seven years to her three, I already knew better than my little sister. I was scowling at her while she swung happily on the disused iron water pump in our garden, when the heavy rusty contraption fell. Her edges were visible in the grass: a pudgy hand, a few toes in white tights. It took all of the family to heave the thing off. There was a lot of blood. I grabbed her head like it was a broken melon and willed the halves together. Stitches and glue were what put her head back together eventually, but I remember, as she scowled at me from a hospital bed, thinking that no stronger force exists than the tense bond between sisters.
Since the start of Stranger Things, Eleven has been a self-contained outsider. A tiny alien who has been defined largely by her non-biological relationship to men: she came from a lab where her "father" was an abusive dictator; in a gang of boys she was finally adored, but was the only girl; then, in the latest season, she finds a second paternal figure in Hopper, who – instead of being a soft presence in her life – inadvertently becomes like the "father" from the lab. Her real mother is in a looped trauma, unreachable, absent.
In episode seven of season two, creators the Duffer brothers give Eleven the greatest gift: an older sister, Kali. Titled "The Lost Sister", the idea that our nosebleeding friend has always had another, more real half than just Mike Wheeler – with whom she has the purist romantic relationship TV has seen in years – makes perfect sense. This breakaway episode has been widely criticised as a basic adolescent rebellion sketch; a failure for using punk aesthetics badly, making clichéd nods to superhero films and diverting from the main storyline. But for its successes and many weaknesses, it should be read as a tale of two sisters.
"What did the girl look like?" asks Eleven's aunt Becky, after Eleven sees flashbacks of the Indian girl she was trapped with at Hawkins lab. "Different" is her answer.
Rather than her skin colour or the fact Kali was snatched from a bed in London, any sister will know the difference between them is more significantly marked by time. When Eleven first finds grown-up Kali in the black box of her psychic travels, she is turned towards a fire. That aggressive heat is what Kali has grown into. Growing up, sisters might be inseparable twins, but as adults it can be like looking into a cracked mirror. You catch glimpses of a primal connection, the earliest moments that shaped the core of who you are, a likeness. Yet, in every word and decision, there's a stranger, informed by the life they've led since you've been apart. It's clear Eleven could have turned out like Kali without the love she'd been shown.
If you ignore the cringeworthy aesthetic of the set and distracting addition of Kali's outsider gang, it's a touching reunion. After Eleven proves her powers, she and Kali expose their thin wrists. An "008" is tattooed on Kali to match Eleven's "011": the same but different. "Sister," they repeat to each other, before embracing.
With all the bossiness of a big sister, Kali tries to bridge the gap between them. She takes Eleven to channel untapped anger into psychokinetic strength, to drag a train carriage towards them. Disappointingly, when flashing through the furious memories of loss and entrapment Eleven has suffered, the ST writers use new female character Max playing innocently with Mike as bait: a lazy betrayal of another kind of sisterhood. But when asked how it felt to join Kali, an exhausted Eleven says "good", and means it.
The hackneyed makeover scene – everyone diving in on Eleven in a chair, plastering her with dark eyeshadow and slicking her hair back with goo – has been discussed by critics as her "teen rebel" phase. For me, it brought back memories of dressing up my sister, her eager to please, testing out a costume that felt a little more me than her. The years she spent stealing my dresses and putting them back in my wardrobe, kohl smudges giving her away. Eventually she came out with my mates, shyly relaxing into the role. It's a dynamic wrapped up in pushing limits, taking what fits and rejecting what feels wrong.
The ultimate test of their sisterly past comes when Kali takes Eleven for her first kill. It's a man called Ray, who has hurt them both, physically harming Kali and giving Eleven's mother enough electroshock to permanently break her mind. Armed and standing in front of a quivering man, they're a picture of strength and unity. He doesn't recognise them until Kali uses her powers to make them appear as the two girls they were when he knew them, a pair of ghosts in their almost-identical navy pinafore outfits. Eleven has learnt well from her big sister – honing their shared ability for magic, a certain hardness – but when it comes to the kill, it's another pair of sisters who stop her short. As Ray's puce head slides across the floor, choked by Eleven's invisible hand, a photo frame comes into shot, of him and his two girls, clearly not much younger than Eleven and Kali. They're discovered next door, wide-eyed and huddled together in matching nightgowns, on the phone to the police.
Kali might have seriously suffered from the weak writing of the whole episode, but she did inadvertently teach Eleven what having a sister meant.
"I was once just like you, you know that? But that's why I'm hard on you, because I see in you my past mistakes," she tells Eleven. In all the mediocre dialogue – and the fact that Kali wants Eleven to stick around for selfish reasons – this summarises well the worst part of being an older sister.
Finding retrospective clarity in a half-remembered childhood – with all its pain, loneliness and the brilliance and lacking of your parents – is something done best with a sister. "Let us heal our wounds together," Kali urges Eleven before she leaves to her real family, Hopper, Mike and the rest of the boys. In this instance, the pair have legitimate trauma to work through. The narrative rejects that possibility for now.
Understandably, Matt and Ross Duffer had to defend this panned episode to irritated fans by saying of Eleven: "Just like Luke Skywalker, she needed to go off on her own and learn something about herself." But sadly Eleven barely began to do that through what bound her and Kali together, and that's the real failing here. This was an isolated bottle episode, and at the very least we needed a fuller origin story that showed their shared history. To lose the punk extras no one cared about to deepen an understanding of the character fans care for the most.
Giving Eleven an Eight could have been the most intriguing psychological storyline of the season – no one holds the broken mirror up like a sister, and there's certainly no one better to save the day – but, unfortunately, the writers took that greatest gift and power away from her.