Supergirl faces her first non-alien nemesis when one of her cousin's enemies--the nuclear-powered Reactron--comes looking to kill her. Meanwhile, Cat runs a derogatory exposé on Supergirl after interviewing the superhero.

Kara finds herself juggling her personal and public lives when she offers to take care of Cat's son Carter, deal with James' relationship with Lucy, and try to stop a bomber who is targeting Maxtech properties.