Ep 4. In Plain Sight

In Supergirl season 5 episode 4, titled "In Plain Sight," Kara Danvers (aka Supergirl) continues to grapple with her secret identity as a journalist at CatCo Worldwide Media while also trying to control her rising fame as a superhero in National City. However, her personal life takes a hit when she discovers her best friend, Lena Luthor, is secretly working on a "project" for her brother, Lex Luthor, who is currently in prison.

Meanwhile, National City is plagued by a new vigilante known as "The Protector," who is going after people who have been arrested by the police but were later released due to legal loopholes. The Protector's actions gain popularity among the city's citizens, who are frustrated with the justice system's shortcomings.

Supergirl investigates The Protector's actions and discovers that he is actually a former cop named Jim Harper, who was fired from the force after speaking out against corruption within the department. Harper blames the system for failing the citizens he swore to protect, and has taken matters into his own hands to enact his own form of justice.

As Supergirl tries to convince Harper to trust in the legal system and stop his vigilantism, Lena's secret project comes to a head. With her brother's help, Lena has created a device that can render a person invisible, and she plans to use it to protect herself and those she cares about from harm.

However, when the device falls into the wrong hands, Lena must confront the consequences of her actions and the true motives behind her brother's involvement. Supergirl must also face the fallout of keeping secrets from those closest to her and decide where her loyalties lie.

Overall, "In Plain Sight" explores themes of justice, loyalty, and the consequences of playing with power. The episode also sets the stage for future plot developments as Lena's actions and motivations are further questioned, and Supergirl navigates the fallouts of her double life.