SPOILER WARNING: This article contains major spoilers for "House of L," the latest episode of Supergirl.
Lex Luthor has a dastardly plan to exonerate himself and become a hero in America's eyes once more. In "House of L," the latest episode of Supergirl, his grand plan to use Red Daughter as a way to manufacture a crisis for him to stop was revealed at last -- and, as it turns out, it has been underway all season long.
After he was sentenced to 32 life sentences three years prior, Lex bided his time, waiting for an opportunity to strike. That moment came thanks to the consequences of the Season 4 finale. When a copy of Supergirl created by Black Kryptonite turned up in Kasnia, he seized his chance to create a weapon molded by his influence.
Using a combination of bribery and threats, Lex took a trip to Kasnia during his prison sentence. The Kasnian military hoped Lex, the world's foremost expert on everything Kryptonian, would help them understand and control Red Daughter's powers. He did that and more. He instilled Red Daughter with a hatred of all things American and, worse, Supergirl herself.
In doing so, he hopes to manufacture a crisis between Kasnia and the United States, where he had already planted the seed of unrest by ordering Otis and Mercy Graves to turn Ben Lockwood into Agent Liberty. However, because he had a hand in all the events leading to this crisis, he would be able to step in to stop it, thus redeeming him in the eyes of the American public. What's more, he'd maintain his prison alibi all the while; after all, there is no better proof of his innocence than the fact he has "been in prison" all along.
To prove how terrible America truly is, Lex brought Red Daughter to National City. There, he showed her examples of America's greed. He even took her to Kara's apartment while she was away in Smallville to show her that Kara lives like "a princess in a tower." Unfortunately for Lex, Red Daughter's American adventure backfired. After reading Kara's journal, she began to empathize with her twin.
In response, Lex sought to break Red Daughter's heart and blame it on the Americans. He staged a false attack on an American warship, which responded with force. Lex made sure the target was the object of Red Daughter's affections: a young boy named Mikhail, who Red Daughter had saved from thieves. She returned to Kasnia to find Mikhail's house destroyed and, believing him to be dead, swore revenge on America and its protector Supergirl.
Then, when Red Daughter fell ill, he sprung into action. He realized the only way to cure her was using his sister Lena's research on Black Kryptonite. Realizing she would never willingly share it with him, he gave himself cancer. This led to his compassionate release; he returned home to push Lena to finish her research and develop a cure. His ploy worked, enabling him to take the cure and develop a few superpowers of his own.
Cured and imbued with enhanced abilities, Lex went to Kasnia, where he gave Red Daughter a blood transfusion. She awoke to find him the process of giving her blood. As she realized what was happening, he told her he cared about her more than she knew. This moment solidified her loyalty to him once and for all.
However, there's one thing he didn't take into account: Otis' compassion. He couldn't bring himself to let Mikhail die. Instead, Lex's lackey took the boy to America and told him to lie low. For now, Lex and Red Daughter are none the wiser. If the Kara clone were to ever find out about Mikhail and the circumstances of his survival, though, it could jeopardize her allegiance with Lex.
Airing Sundays at 8 p.m. ET/PT on The CW, Supergirl stars Melissa Benoist as Kara Danvers, David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen and Chyler Leigh as Alex Danvers.