Desperately in need of comfort following her broken engagement, Alex travels with Kara back to her hometown of Midvale. While there, Kara recalls the incident from their childhood which turned two strangers into sisters.
The TV series Riverdale (murder mystery in a small-town high-school setting), Smallville (teenager with superpowers in a small town dealing with mysterious events, mention of Chloe and the "Wall of Weird"), Nancy Drew novels (teenage girl detective adventures) and the movie Twilight (the visuals of Kara jumping through the woods)
Even in a small-town high-school, it's unlikely that Kara and Alex would be in the same history class, given the two-year gap in their relative ages.
With long-lingering shots, the direction gives away the identity of the killer long before the audience has a chance to deduce it based on the clues offered.
Izabela Vidovic and Olivia Nikkanen do a phenomenal job as the younger versions of Kara and Alex.
It's a brief thing, but David Harewood gets a good quick moment of silent acting looking very broken up after he changes back to his Hank Henshaw form after talking to Kara as "Noel Neill". It really hits you in that moment how seriously, even back then, J'onn took his promise to look after Jeremiah Danvers' children. It's especially touching given that "Noel" said she couldn't imagine what it was like to lose your whole world in the same way Kara did when J'onn doesn't have to imagine it yet can't give Kara any comfort beyond a sympathetic ear.
The episode title - Midvale - comes from the city where Alex and Kara grew up in The DCTVU.
In the DC Comics Universe, Midvale is a small suburb just outside of Metropolis. In the Silver Age, Midvale was the town Kara Zor-El settled in upon her arrival on Earth, where she lived in the Midvale Orphanage until she was adopted by The Danvers. Most of the Supergirl movie was set in Midvale as well, where Kara Zor-El attended the Midvale Boarding School.
The building used for the exterior shots of Midvale High in this episode - Templeton Secondary School in Vancouver - was also used to depict Smallville High on the series Smallville and is currently used to depict Riverdale High on the show Riverdale.
Mention is made of Lex Luthor being brought to justice by Superman for selling something called "Lexosuits.". In the classic comics, the power armor which Lex Luthor constructed in order to fight Superman physically was often called a Lexosuit as a play on exo-suit, which is used to refer to any form of powered exo-skeleton.
Mention is made of Superman wearing red underwear over his tights in this episode - a detail his costume lacked when we saw him during Supergirl's second season. This is, of course, a classic detail of Superman's original costume, mirroring the modesty garments worn by the circus strongmen Superman's classic costume was modeled on in the 1930s. The New 52 redesign of Superman's costume lost these trunks, opting instead for simple blue pants.
Kara's first friend as a teenager, Kenny Li, may be a double nod to the original Superman comics. In the comics, before being adopted by The Danvers family, Kara Zor-El used the alias "Linda Lee" while living at the Midvale Orphanage. Kenny Braveman was the name of a boy born on the same day that the rocket carrying baby Kal-El to Earth landed in Smallville. Kenny and Clark would become friends at a young age, rivals in high-school and Kenny would eventually become the villain Conduit in his efforts to prove himself Clark's better.
The sequence in which Kara jumps through the forests of Midvale seems to have been inspired by a similar sequence in the film adaptation of the book Twilight.
Kara makes reference to Clark having a friend named Chloe who loves weird tech stuff and has a "wall of weird". This is a nod to Chloe Sullivan - a character from the TV series Smallville.
The FBI agent who tries to scare Kara straight regarding using her powers gives her name as Noel Neill. This is the name of the actress who played Lois Lane in the 1948 Republic Superman serials and the 1952 television series Adventures of Superman. As a double-play on the reference, she is played by actress Erica Durance, who played Lois Lane on Smallville.
Kenny Li developed Galileo - a computer program that took images from his telescope and capture it as digital photographs on his laptop.
Eliza: This is the mom fine print - when your child is in agony, you show up regardless the hour.
Eliza: You have the most wide-open heart in the world for other people. But when you feel weak, you punish yourself for it. You've had an awful year-
Kara: And I'm feeling a lot better. I promise.
Eliza: You don't have to be better. You're allowed to be a mess.
Kara: But too many people depend on me.
Eliza: That is a great excuse.
Kara; Do you want to talk about it? It might help.
Alex: (sighs) You don't get to do that.
Alex: You don't get to shut down - what - for six months after Mon-El goes? And then, now, sit here, and you tell me to talk.
Kara: It will get better.
Alex: Yeah? Are you better?
Young Kara: I remember my parents! I remember Krypton! I remember being alone in that pod and not knowing if I was going to see anyone ever again! And then I landed here! And no one asked me if I wanted these powers. But I have them! And all I want to do is help people with what I've been given and no one will let me!
Sheriff Collins: You're real brave. Not even screaming. Not that anyone can hear you.
Young Alex: Someone's listening right now.
(Cut to Kara, flying at super-speed towards the high-school.)
J'onn loans his spaceship/vintage car - last seen in 304 - to Alex and Kara for their trip.
Kara and Alex shared a room as teenagers.
Alex was in AP Math during her senior year.
Kryptonian children study calculus at the age of four.
Kara found math and science easy in school. She found history pointless.
Superman first brought Lex Luthor to justice sometime ten years earlier, because of Lex selling something called Lexosuits.
Alex was part of the cool crowd and hung out with the high-school quarterback.
Kara only had one friend in high-school - a nerdy kid named Kenny Li.
Kenny secretly tutored Alex in calculus.
Kenny stumbled across multiple crimes using his Galileo program. These included the quarterback smoking pot, a student (Josie, Alex's best friend) having an affair with a teacher (Mr. Bernard) and the Midvale sheriff (Sheriff Collins) taking bribes.
J'onn visited a young Kara in the guise of FBI Agent Noel Neill, modeling her on the appearance of Kara's mother.
Clark's friend, Chloe, helps Kara with getting the pictures off of Kenny's laptop.
Kara and Alex were given Kenny's telescope as a gift from Kenny's parents for finding his killer. It still is set up on the balcony at Eliza Danver's house.
Alex was outcast from the popular crowd after outing Josie's affair with a teacher and the quarterback's pot-smoking.
Kara discovered after the fact that Kenny had taken a picture of her flying but never shown it to anyone.
The town of Midvale, ten years earlier.
The Bottom Line
Much better than most flash-back episodes and easily the best episode of Supergirl's third season. The actors playing young Alex and Kara are perfectly cast, truly looking and acting like younger versions of Chyler Leigh and Melissa Benoist. The actual mystery at the heart of the episode is blindingly obvious but the acting more than makes up for it.