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.
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'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 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.
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.
