The Anti-Monitor, the Monitor's evil counterpart, is released into the DC Multiverse and begins to destroy the different Earths that compose it. The Monitor attempts to recruit heroes from across the Multiverse to fight back.

Kara, devastated by the loss of Krypton, struggles to adjust to her new life on Earth. Superman mentors her. Meanwhile, she must contend with a mysterious group called the Dark Circle who searches for a powerful weapon held in the Academy's vault.