Superman discovers a powerful and menacing force headed toward Earth: Brainiac, a super-intelligent alien intent on consuming and destroying entire planets. Accompanied by his cousin Supergirl, Superman ventures into space to confront Brainiac. As he explores Brainiac's ship, Superman learns of Brainiac's horrific methods and witnesses shrunken cities from various planets, including the Kryptonian city of Kandor, which Brainiac had stolen before Krypton's destruction. This discovery holds a personal significance for Superman, galvanizing his resolve to put an end to Brainiac's reign of terror.

Back on Earth, Lois Lane navigates the dangers posed by Brainiac's approaching threat while maintaining her relationship with Superman amidst the chaos. Meanwhile, Supergirl grapples with her traumatic memories of Brainiac's invasion of Krypton, adding emotional depth to her fight alongside her more experienced cousin. With Earth next on Brainiac's list, Superman and Supergirl must combine their strength and intelligence to outsmart the seemingly invincible foe. The stakes are higher than ever as they engage in a dire battle to protect their adopted home and the universe from Brainiac's insatiable hunger for knowledge and destruction.