Seg learns that his home planet of Krypton has been targeted by the world-consuming alien known as Brainiac, so that his future grandson - the greatest hero of all time - will never be born.

After suffering a tragedy, Seg adjusts to the realities of his mission, as well as his newfound rank in the Guilded class, and a new threat. He vows to direct all of his energy toward saving Krypton from Brainiac - as the last son of House El.

During the chaotic Black Zero crackdown on Seg's home district known as the Rankless Initiative, Seg and Adam race to find Brainiac's deadly Sentry, while Lyta-Zod juggles her position as Commander with her love for Seg.

To quell Rankless unrest, the Voice of Rao begins Kandor's Nova Cycle festival and finds a scapegoat for the failed Rankless Initiative. Meanwhile, Seg is approached by a mysterious Black Zero leader.

Fighting for survival within the heart of Black Zero, Seg finds a window into Krypton's ancient past, but learns that his life may be in danger. Meanwhile, Jayna-Zod grapples with her torn loyalties as she considers an offer from House Vex.

Seg is confronted with an impossible decision that will shape the future of the El legacy and the entire universe: stop Brainiac from bottling Kandor or let Krypton perish - so Superman may live.