Amy organizes a community service event, but it's jeopardized by Jeff's return and Glenn's desire to help his co-workers. Meanwhile, Sandra confronts Jonah about his strategy for soliciting donations, and Garrett tries to prove his intelligence to Dina.
Kara's two identities are stretched thin when Supergirl must protect National City from a series of bombings and Kara is tasked with babysitting Cat's son, Carter (guest star Levi Miller). Also, James is conflicted when his ex-girlfriend Lucy Lane (recurring guest star Jenna Dewan Tatum) seeks to rekindle their relationship.
Kara must find a way to free her friends when Non and Indigo use mind control to turn National City's citizens into their own army.
While James's relationship with Lucy reaches a crossroads, Kara travels to Superman's Fortress of Solitude in hopes of learning how to defeat Indigo (guest star Laura Vandervoort), a dangerous being with a connection to Kara's past, who can transport via the Internet.
Kara faces off against her mirror image when Bizarro (guest star Hope Lauren), a twisted version of Supergirl, sets out to destroy her. Also, Kara grows closer with Cat's son, Adam.
