Supergirl: Season 4 (2018)

In the Season 4 premiere, Kara welcomes a new cub reporter to CatCo. Meanwhile, James and Lena argue about James' impending indictment for acting as the vigilante Guardian, while Alex and Brainy struggle to get in sync at the DEO. Supergirl is called into action when remnants of the anti-alien terrorist organization Cadmus try to assassinate pro-alien leaders, but their endgame turns out to be much more sinister than she expected.

A shocking revelation causes chaos in National City. Supergirl sets out to capture Mercy Graves, while Alex takes control at the DEO. Back at CatCo, Kara decides to write an investigative story on Mercy and asks Lena if she can interview her as Mercy has ties to the Luthors. Meanwhile, Brainy meets Nia and the two end up in a precarious situation.

Ben Lockwood did not always hate aliens. Ben slowly transforms from a mild-mannered professor into the villainous Agent Liberty of today through a series of events and input from his anti-alien father.

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 he realizes there are a lot of ways to help his fellow aliens during this tumultuous time.

Colonel Haley makes a surprising decision regarding Supergirl. Kara writes s series of articles highlighting aliens in National City in the hopes that humans will stop being so fearful of them. Unfortunately, the article puts some of the aliens in harm's way.

Everyone gathers for Thanksgiving but 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. Lena kicks off her first set of trials.

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.

Supergirl, the Flash, Green Arrow and Superman engage in the battle of their lives.