Kara's spin class with Lena is rudely interrupted when a cargo ship is attacked by what Kara can only describe as a "shimmer."
Colonel Haley is displeased with Supergirl tampering with the scene of a crime as she's no longer a DEO employee. She orders her to save the heroics for trains and kittens unless she's willing to give up her secret identity.
Supergirl obliges but continues to help Alex from the sidelines when she realizes that there is a cover-up happening.
Eventually, the sisters realize the suspicious alien is actually a "Mortae."
Haley along with two other agents trained these alien children to be killers.
When the President ordered them to cut ties with all alien beings, they attempted to kill the Mortae, but found that it angered them.
They retaliated by trying to kill the three agents who spearheaded the project thus the attack on the cargo ship.
Alex confronts Haley who reminds her that her anger is misguided since aliens are not human beings.
As the remainder of the DEO prepares for a Mortae attack, Haley isn't at all phased by being a target and continues her crusade against Supergirl.
One by one she asks every DEO employee to give up her real identity and eventually, one of them does.
Haley expresses her disappointment at Alex for undermining everything the DEO stands for in order to protect her sister, but there isn't much time to exchange nice pleasantries because the DEO is under attack.
As the Mortae close in on Haley, Supergirl comes to her rescue. You'd think Haley would be grateful but instead, she rubs her newfound knowledge into Supergirl's face.
Alex becomes fed up with Haley's controlling attitude and punches her in the face.
They call J'onn in hopes that he'll mind wipe Haley from remembering that she learned Supergirl's identity.
Even though it is a type of violence, J'onn agrees.
However, the next day, Haley is back at her quest, this time bringing in a "truth seeker" to question everyone at the DEO.
Alex knows there's no way to get away with a lie when it comes to the "truth seeker" so J'onn erases everyone's memories of Kara.
And that means Alex must also erase any memory that connects Supergirl to her sister.
Kara is sure there has to be another way, but Alex assures her that this needs to be done.
As J'onn is wiping Alex's mind, Haley begins her interrogations.
Meanwhile, J'onn is busy opening up his P.I firm under the name "John Jones."
In an attempt to help Supergirl, Brainy reaches out to Nia Nall to get "food" with her.
Nia assumes it's a date, but realizes rather quickly that Brainy wanted to meet with her to persuade her into using her powers to help Supergirl fight crime.
Lena and James kiss and make up after their fight, but it seems a new one may be on the horizon after Lena confesses to creating superhumans.
James promised to be more open to her ideas, but is he really okay with giving normal humans superpowers?