When a new teenager from Krypton named Kara (Summer Glau) finds herself in Gotham Harbor, Batman (Kevin Conroy) and Superman (Tim Daly) quickly discover her impressive skills. It gets even more personal when Superman discovers that the young girl is actually his cousin. Things go bad quickly when the evil Darkseid (Andre Braugher) learns of the new and powerful young girl, and decides to abduct her and take her back to Apokolips. Batman and Superman are on Darkseid's tail, however, determined to do whatever they must to get Kara (known also as Supergirl) back from the evil she has been brought into the middle of.