Mon-El wakes up and escapes the DEO.
The president is coming to tour the DEO and wants Supergirl to meet her on the tarmac.
An attack is made on the president and Supergirl saves her. Kara and Alex gather evidence, and Kara suspects Mon-El. Alex meets Detective Maggie Sawyer.
Kara is assigned to interview Lena Luthor. Lena shows Kara a device that can tell if someone is human or alien.
Winn pinpoints the location of Mon-El. Alex arrives with agents and finds Maggie, who knows she's DEO.
Snapper criticizes Kara's story for being too biased. He tells her to re-write it without her personal feelings.
Maggie invites Alex to meet her at a bar that's a safe haven for aliens. They get some information on their missing alien.
Winn tracks him down again and Kara goes after him. Mon-El is from Daxam, a sister world of Krypton. The two planets did not get along.
Kara questions him, and he denies the attack, but they don't believe him.
Lena tells Kara how she tried to bring Lex back to the side of good, but some people are just bad.
The president is attacked again when signing the agreement. She gets away, but Maggie is taken.
Alex recognizes the attacker from the bar. She goes back for information.
Kara and Alex save Maggie and take down the alien, with Maggie's help.
Kara apologizes to Mon-El for making wrong assumptions. Kara breaks the news to him that his home planet is gone.
The president turns out to be an alien.
J'onn checks out the alien bar and meets another Green Martian.