Falling

"Falling" is the sixteenth episode of the first season of Supergirl. It aired on March 14, 2016.

Synopsis
Kara turns on her friends and the citizens of National City after being exposed to Red Kryptonite which makes her malicious, dangerous, and mean. Also, Cat Grant appears on THE TALK to discuss Supergirl.

Plot
Cat appears on CBS' "The Talk" to discuss her relationship with Supergirl, and goes out of her way to praise her. Kara hears a little girl wearing a Supergirl outfit being bullied. She flies down to them, calls her a friend, using X-ray vision to find out her name, to the other kids' amazement.

Kara was watching the show when Cat interrupts, reflecting on how well it went, and told her to find Winn. She thinks he's hiding in the storeroom, but when she uses her X-ray vision, she discovers him making out with Siobhan.

Cat tells Kara that Lucy has quit. When she goes to James he said she broke up with him because he had a chance to tell her that Kara is Supergirl, but denies the break up as having anything to do with Kara or Supergirl.

Alex and Kara discuss the issue. Kara says she feels guilty and that she doesn't want to be a rebound girl. Alex attempts to make her feel better and cites "Kim and Kanye" to Kara's embarrassment. Alex Miranda Crane comes to the DEO to personally congratulate Hank, Alex and Kara for their efforts to fight alien threats. She plans to lobby for grater funding for their agency.

Kara flies out to help a fireman trapped by debris in a fire. She manages to lift the debris off him. As she is about to leave, she staggers briefly, her face suddenly having glowing red veins, which quickly vanish. Shrugging it off, she flies off, not seeing the glowing red object underneath nearby debris.

The next day, Kara smashes her alarm clock and arrives for work at CatCo wearing somewhat more stylish attire than normal. It turns out that Lucy left the company, and Cat wanted Siobhan to search for replacements. However, Kara already took care of it.

Later that day, Hank briefs the DEO team on a gang of bank robbers who have turned to a Fort Rozz escapee, a K'hund, for added strength, though Kara does not seem interested. That night, the DEO engages the K'hund and, as planned, they lure him toward Kara to finish him off. Kara easily gets the better of him, crushing his hand and stepping on his throat. However, she lets him go, saying he isn't worthy of her time. Hank and Alex know this isn't like Kara, but when they confront her, Kara lays into Hank for hiding his identity.

The next day, Siobhan reveals that she managed to get footage of Supergirl letting the K'hund escape. She tries to pitch it to Cat, but Cat isn't interested. Undaunted, Siobhan plans to sell the story to her old employer, the Daily Planet. However, Kara picks up her plotting with her super hearing, and lures Siobhan away from her desk long enough to print a copy of the email. When Cat learns about Siobhan's treachery, she fires Siobhan on the spot.

Kara invites Winn and James to celebrate at a club. Kara arrives late, and persuades James to dance with her. She tries to come on to James, and trashes Lucy in the process. James and Winn realize that Kara isn't herself.

Kara later flies to CatCo, and tells Cat she's no longer interested in being a hero. To prove her point, she hurls Cat off the balcony, and flies down to catch her just in time.

James and Winn alert Hank and Alex about the changes in Kara. Hank cross-references Kara's last missions, and discovers the red substance at the fire site. Just as they wonder what it is, Maxwell arrives and admits it was his creation.

While Maxwell is in custody, he admits that the substance was Red Kryptonite. He created it in hopes of stopping Non's next attack--only to find out that it backfired disastrously and turned Supergirl bad. He does, however, offer to make an antidote.

Cat reluctantly goes on air to declare that she can no longer stand behind Supergirl.

Alex tracks Kara to her apartment, and finds Kara wearing a black uniform similar to what Astra, Non and their army wear. Kara lays into Alex, pouring out years of resentment. Alex warns her that she isn't herself. However, Kara is now mad with power, and says she feels freer than she ever did. Vowing to make those who don't already worship her do so, she flies off.

Senator Crane convinces the DEO that Supergirl is now a threat. Reluctantly, Hank dispatches a team to track down Kara. Maxwell finishes his antidote, and loads it in a gun for Alex.

The DEO arrives to find Kara wreaking havoc on National City. Alex tries to talk some sense into Kara, but Kara violently attacks Alex. Seeing Alex in danger, Hank turns into J'onn J'onzz and engages Kara, distracting her long enough for Alex to fire the antidote. Hank is taken into custody.

Kara comes to, and is horrified at what she did; she couldn't stop it. Alex admits there was some truth to what Kara said, but promises to work on it.

Hank tells Senator Crane that he is J'onn J'onzz. Crane feels betrayed and walks out. Alex wonders why Hank didn't run, but Hank said he would do anything to keep Alex and Kara safe.

Kara tries to apologize to James, but James needs some space for awhile. Later, as Supergirl, Kara offers to apologize to Cat, but Cat tells her that she needs to win back National City's trust first.

Trivia

 * In the comics, Red Kryptonite originally had a different effect on Superman every time he was exposed to it.
 * The Khunds were originally introduced in the comics as enemies to the Legion of Super-Heroes.
 * Siobhan sends an email to Perry White, head of the Daily Planet.
 * There is a scene where Kara dumps a bowl of peanuts onto a bar-top and begins to flick them, breaking bottles with them. This is a direct homage to the the movie Superman III where Christoper Reeve's Superman does the same thing under the influence of synthetic kryptonite.