WARNING: The following contains major spoilers for "Confidence Women," the latest episode of Supergirl, with premiered Sunday on The CW.

As Lena Luthor's secret revenge plot against Kara Danvers continues in Season 5, she sold her controlling interest of CatCo to former colleague Andrea Roja. She, in turn, tasked her trusted associate William Dey to investigate Supergirl, having hinted at a villainous past of her own. This week's episode, "Confidence Women," reveals the rocky history between Lena and Andrea, while confirming the latter is a bona fide supervillain.

Lena and Andrea are revealed to have met at boarding school, and bonded over a mutual love for Titanic. Years later, both women are at a crossroads with their respective family businesses: Lena is fired for refusing to aid her older brother Lex in his obsessive quest to kill Superman and Maxwell Lord -- a recurring antagonist in Supergirl Season 1 -- and in developing a new phone that threatened to put the Rojas out of business. Desperate to escape their professional woes, the two old friends decide to explore the Costa Rican rainforest in search for the Acrata Medallion, a mythical relic beleived to control shadows.

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Lena's dying mother had recounted the medallion's legend to her as a child, and she hoped to recover it to stop Lex from using its properties to unleash Kryptonite into the Earth's atmosphere. Andrea stumbles into a cave where she discovers the medallion, safeguarded by an old man in a Legend of Zelda-esque twist. The man knows much of Andrea's background, and offers her the medallion in exchange for service at an undisclosed point in the future. Agreeing, Andrea claims the medallion for herself while Lena subsequently is heartbroken believing it to be lost to the ages when she enters the cave herself.

Upon her return to civilization, Andrea learns Lord's phones have suddenly malfunctioned around the globe, and her family company Obsidian has rebounded significantly. After seeing Andrea wearing the medallion at a social gala, however, a betrayed Lena ends their friendship before breaking up with her boyfriend and moving to National City, cuing up her introduction in Season 2. Meanwhile, Andrea learns the clandestine organization Leviathan is linked to the medallion, and she's forced to use the powers within the relic to transform into the supervillain Acrata.

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Now in the relative present of Season 5, Andrea -- under the Acrata persona -- reluctantly teams with Lena to free Russell, the villainous Rip Roar who debuted in the previous episode, from DEO custody. Russell is revealed to be in a romantic relationship with Andrea, while Leviathan fears their agent will reveal his secrets to the government organization. Lena uses new technology to brainwash most of the DEO -- save Alex Danvers -- while feigning an attack from Acrata to Supergirl to position Kara to take on Andrea herself.

While Supergirl is predictably able to save the day, Acrata succeeds in escaping while Russell is executed by Leviathan. Kara's boss is revealed as National City's shadowy, new villain, although she is still unaware of the full extent of Andrea's villainy. And, all the while, Lena continues to showcase herself as every inch as manipulative as her brother, as she researches the medallion and Leviathan.

Airing Sundays at 9 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.

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