When multiple children get sick from lead poisoning, Morgan Edge points the finger at Lena and blames her creation of the lead bomb she made to save National City from the Daxamites. While Lena knows she never intended any harm, she fears there may have been a flaw in her design, leaving her responsible. Kara teams up with Samantha to clear Lena’s name, but it turns out to be harder than they thought. Meanwhile, Alex and Maggie make a crucial decision about the future of their relationship.
Kara investigates a secretive new group whose leader, Thomas Coville, has a mysterious connection to Supergirl. Meanwhile, Samantha feels like she’s letting Ruby down, and J’onn confesses an old secret.
Psi, a thief with psychic powers, attacks National City. Able to immobilize people by tapping into their worst fears, Psi proves a formidable opponent for Supergirl. Meanwhile, James and Lena are at an impasse, and Samantha starts her new job at L-Corp.