After the Worldkillers have been dealt with Kara's life is finally in a place resembling normal. She has a great girlfriend in Lena Luthor, her older sister is dating Sam Arias and is the director of the DEO after J'onn stepped down. But this is all about to come crumbling down when a new villain bursts onto the scene. He's an evil meta-human with superspeed from Earth-1 which is Barry Allen's earth where Barry Allen is known as The Flash another meta-human who uses his superspeed to help others. Who is this evil meta-human? He is known as The Reverse-Flash Barry Allen's worst enemy. How did The Reverse-Flash end up on Kara's earth and what is he up to?