Ever since Supergirl began, its heart has been centered around the most important relationship in Kara Danvers’ life—not her superheroic duties carrying on in her cousin’s shadow, not her myriad love interests, but the bond she’s shared with her adoptive human sister, Alex. Now, that relationship has gone through a hell of a change.
A major theme on this season of Supergirl has been a... let’s say less than subtle commentary on xenophobia and bigotry, as No-Sir-Definitely-Not-a-MAGA-chud Agent Liberty stoked the flames of hate and mistrust against Supergirl and aliens in general in the midseason finale, leading to a pretty shitty situation where not only is Supergirl at odds with the DEO (making Alex’s job vastly more difficult), but Kara has been forced to suddenly and harshly deal with the fact that her secret identity is actually still really important beyond her immediate circle of friends.
It’s kind of hilarious given how completely and utterly lackadaisical the show has been for the vast majority of its three-and-a-half seasons so far when it comes to how it treats Kara’s secret identity. I mean, yeah sure, there may be scientific evidence that the age old “act mild-mannered and put on a pair of specs” disguise she and Clark adopt could work. But these people have been yelling Kara’s name out in Supergirl’s general direction for so long it’s kind of insane that “Suspicious Minds” wants us to believe that just a handful of DEO agents actually know that Kara Danvers is Supergirl. But the episode makes it work—if with a pretty arbitrary conceit—by making Alex and Kara have to face an awful, heartbreaking choice together.
After new DEO boss Colonel Haley reveals to Alex that she’s realized her sister is really the Girl of Steel, the Danvers kids call in J’onn to wipe Haley’s memory of the revelation, buying approximately 15-20 minutes of peace, when the mind-wiped Haley decides that she’s gonna bring in a super-duper alien who can compel the truth out of anyone, and use it to interrogate the entire DEO staff about Supergirl’s identity. Knowing that they can’t beat the alien’s abilities, the agents that do know Kara’s identity all agree to having their memories wiped by J’onn to avoid giving up her secret...Alex included.
It’s an incredibly tragic moment for Kara, one played to a tender, heart-wrenching perfection by both Melissa Benoist and Chyler Leigh as Alex wrestles with the idea of having to no longer share a secret her sister has shared with them since they were kids. Kara and Alex would still be sisters after J’onn works his martian man-magic, but the bond the two sisters have forged so strongly is built on Kara having let Alex into her wonderful superworld. And, in an interesting moment, it presents an extra layer of tragedy to the plotline we saw Kara go through in “Elseworlds, Part 3”—which at the time felt like an arbitrary bit of dramatic padding—where she found herself in an altered reality where Alex existed, but wasn’t actually her sister. While the alt-Alex of “Elseworlds” was easily convinced to help Kara, Kara knows she can’t do that with her sister now without threatening both of their lives.
And so “Suspicious Minds” ends with the handful of DEO Agents that once knew who Supergirl really was getting their brains wiped—with Alex going last, a fate neither Kara or the show itself is capable of witnessing as the credits cut in. Time will tell just how long Supergirl will keep this dramatic evolution of Alex and Kara’s relationship going—and what the fallout could possibly be when or even if Alex re-learns who her sister is behind her glasses. But for now, more than it has since even the show first started, Supergirl’s secret identity actually, truly matters.