Supergirl

In the season four premiere, Supergirl (MELISSA BENOIST) is called into action when remnants of the anti-alien terrorist organization Cadmus try to assassinate pro-alien leaders.

A shocking revelation causes chaos in National City. While Alex takes control at the DEO, Supergirl sets out to capture Mercy Graves (recurring guest star RHONA MITRA). Back at CatCo, Kara decides to write an investigative story on Mercy and asks Lena to introduce her as she has ties to the Luthors. Meanwhile, Brainy meets Nia and the two end up in a precarious situation.

Ben Lockwood (SAM WITWER) didn't always hate aliens. Through a series of incidents, and input from his anti-alien father (guest star XANDER BERKELEY), Ben slowly transforms from a mild-mannered professor into the villainous Agent Liberty to today.

When Supergirl needs help, Alex asks Lena and Brainiac to team up. Meanwhile, J'onn questions his decision to quit the DEO. However, after running into Manchester Black (guest star DAVID AJALA), he realizes there are a lot of ways to help his fellow aliens during this tumultuous time.

Colonel Haley (new series regular APRIL PARKER JONES) makes a surprising decision regarding Supergirl. Meanwhile, Kara writes a series of articles highlighting aliens in National City in the hopes that humans will stop being so fearful of them. Unfortunately, the articles put some of the aliens in harm's way.

Although everyone gathers for Thanksgiving, Kara is feeling down after her televised debate with Ben Lockwood about the anti-alien sentiment coursing through National City. Meanwhile, James and Lena argue about the best way to handle the Children of Liberty.

James falls in deeper with the Children of Liberty in his efforts to meet Agent Liberty. Meanwhile, Supergirl and Manchester Black follow a lead on Agent Liberty's location, but things take a dark turn. And Lena kicks off her first set of trials. Chad Lowe directs.

In the midseason finale, Nia has a powerful dream about Agent Liberty, but refuses to look at it as a prophetic dream and pushes it aside. After noticing something is bothering Nia, Kara enlists Brainy's help, and the two try to persuade Nia to embrace her destiny. Meanwhile, Manchester Black pays Ben Lockwood a menacing visit. Kevin Smith directs.

In the final part of the three-part crossover, Supergirl, The Flash (guest star GRANT GUSTIN), Green Arrow (guest star STEPHEN AMELL) and Superman (recurring guest star TYLER HOECHLIN) engage in the battle of their lives.

Upset that Supergirl won't step aside or take orders, Colonel Haley refocuses her energy on finding Supergirl's true identity and interrogates all DEO agents - including Alex.

Kara joins Nia on a trip to Nia's hometown to visit her family during the town's annual Harvest Festival. While home, Nia's mother, Isabel (guest star KATE BURTON), encourages her daughter to embrace her destiny. Meanwhile, Alex deals with a dangerous street drug that is turning people violent and giving them temporary superpowers.

When Kara teams up with J'onn on his latest assignment as a P.I., it unfortunately ends up tying directly into Alex's current DEO investigation, involving the villain Menagerie.

When Manchester Black breaks out of prison with the help of his new team, The Elite, who are set on punishing the anti-alien forces, Supergirl pulls double duty as she tries to apprehend Manchester Black and his team as well as dealing with a shocking new development with Ben Lockwood.

When Ben Lockwood and The Elite stir up trouble at an anti-alien rally, Supergirl is forced to take a stand.

Secretly furloughed from prison due to failing health, Lex Luthor (JON CRYER) visits his sister, Lena, to seek her help finding a cure, but Lena's suspicious of his motives.

In the wake of Lex Luthor's return, the show flashes back to what he's been doing for the last two years and how his secret machinations and plans have affected Supergirl and Lena.

Shocked at what Lex has created, Supergirl faces her biggest challenge yet as she deals with the destructive aftermath of his nefarious plans.

While Supergirl and Lena search for clues on how to defeat Lex, Alex faces off against Ben Lockwood after he storms the DEO to acquire some weapons to hunt Supergirl.

As Kara doggedly works as a reporter to clear Supergirl's name, Dreamer picks up the slack as National City's protector, which leads to a showdown with Ben Lockwood. James takes drastic measures to relieve his PTSD. Series star David Harewood directs.

Kara and Lena head to Kaznia to hunt down Lex. However, Eve Tessmacher (recurring guest star ANDREA BROOKS) sets a trap for the duo that could ultimately reveal that Kara is Supergirl. Meanwhile, Alex gets a long-awaited phone call, James practices using his powers, and Ben Lockwood takes a dangerous stand inside the DEO.

Kara comes face to face with Red Daughter and the two engage in an epic battle. Determined to find a way to extract the Harun-El, Lena turns to an unlikely source for help - Lillian Luthor (guest star BRENDA STRONG). Meanwhile, Alex realizes she's missing parts of her memory; And Brainy, Nia and J'onn set out to track down aliens who have been abducted by Lex.

In the fourth season finale, Lex Luthor descends upon Washington, D.C. and summons Lena and Lillian Luthor to the White House. Realizing that she's got one last chance to stop Lex, Supergirl turns to the power of the press to help her.