Spoilers ahead for Episode 18 of Supergirl Season 3, "Shelter from the Storm."
The main conflict of Supergirl Season 3 has revolved around Supergirl and the Worldkiller known as Reign. In the last few episodes, however, another conflict has developed between a pair of characters who were once the best of friends. Kara and Lena aren't quite on the same page any more, and Lena is arguably one of the most dangerous characters on the show thanks to her intelligence, her resources, and her ruthlessness. "Shelter from the Storm" ended on a scene that may have hinted that Lena has figured out that Kara and Supergirl are one and the same, and that could be very bad for everybody.
The trust between Lena and Supergirl was damaged as soon as Supergirl learned that Lena was harboring and experimenting on Sam/Reign, and Supergirl felt compelled to ask James to break into Lena's lab and check for any spare kryptonite. For her part, Lena understandably felt betrayed when James 'fessed up that Supergirl wanted him to sneak behind her back. The conflict only escalated in "Shelter from the Storm" when Lena informed Supergirl that she'd learned the formula for creating kryptonite and had created some specifically designed to take down Reign.
Supergirl didn't back down from her stance that she and she alone should have control over the kryptonite on Earth, and Lena didn't agree to hand over her formulas and stash. Supergirl seemed willing to bury the hatchet by the end of the hour after Lena's kryptonite was instrumental in capturing Reign, but Lena wasn't quite so willing to forgive and forget, and her final conversation with Kara (not as Supergirl) may have been a clue that Lena knows the truth about Kara.
The two former BFFs met up in an elevator on the way up to visit Ruby, who was dealing with the fact that her mom was the supervillainess Reign. Lena started chatting about how she and Supergirl aren't getting along and that it's never a good idea to meet your idols. Lena was clear that she believes she can never trust Supergirl again, citing the fact that Supergirl tried to use Lena's personal relationship with James against her and arguing that Supergirl just isn't who she seemed to be. When Kara tried to protest that Supergirl must have had a good reason, Lena gave her some looks that didn't just seem like those of a friend venting to another friend. Lena's expression seemed more like that of somebody who knew a very big secret and was giving Kara the chance to come clean.
All things considered, it would make sense if Lena had figured out that Kara is Supergirl. For one thing, Kara looks exactly like Supergirl if Supergirl wore glasses, and the two are never in the same place at once. Lena grew to count both as friends, and she's a brilliant woman. If anything, it's been difficult to believe that Lena hasn't figured out that Kara is a Kryptonian. The events of "Shelter from the Storm" combined with Katie McGrath's performance in the elevator scene mean that it wouldn't be completely out of the blue if Supergirl reveals that Lena knows the big secret.
If Lena truly has figured out that Kara is Supergirl, Kara is going to need to come clean to Lena if she wants to salvage the friendship and perhaps stop Lena from embracing her Luthor side and going full villain. Lena will never trust her again if she doesn't tell the truth. Admittedly, Lena might be a dangerous person to trust with the Supergirl secret at this point, but she deserves to know the truth. Even if Kara is the hero of the show and has always had the best intentions in her interactions with Lena, she has lied to her friend from the very beginning. If Lena does end up going full villain, we can probably trace her passing the point of no return to "Shelton from the Storm."
New episodes of Supergirl air on Mondays at 8 p.m. ET. Supergirl may have already gotten the renewal order, but not all shows have been so lucky. Check out our list of big network TV cancellations for the shows that have already gotten the axe, and be sure to check back with CinemaBlend's rundown of TV renewals and cancellations. Our schedule of TV season finales is worth a look, as is our summer TV premiere schedule for what you can watch in the not-too-distant future.