On the Spaceship,Starro the Conqueror & his Gladiator,Despero plan to invade earth when they get a distress signal from here.
At Gotham,Batman stops the robbers,who had alien starfishes on their faces. He contacts Clark & suggests that they need a team. They found 4 other heroes,who fought off the invasion. They decide to work together along with J'onn J'onzz,who is also called Martian Manhunter.
They search for the source and confronts Starro & Despero,who are feeding People's conscious to the Giant Starro. Despero reveals that the Conqueror's real name is Cobi from the planet,Hatoreian & he was in control by the Giant. The Heroes battle them. The Flash quickly free the Mind Controlled people & Green Lantern gets them to safety. Martian Manhunter manage to free Cobi & Wonder Woman defeats Despero,but the Giant has awoken.
The Heroes fought against it. Superman blasted one of his limbs with his heat vision. Batman uses the smoke grenade to weaken him,allowing Aquaman to hurl the Trident at the Giant's eye,killing him. Cobi thanked the heroes & return home while Despero was taken into custody. The People congratulates the heroes,who are now called "The Justice League".
Mid-Credits:
Bruce takes Starro's severed limbs that was shrunk to Wayne Manor where it regenerate into a new body.
Post-Credits:
Lex Luthor went inside Zod's ship where he heard a voice saying "Hello,Lex Luthor. I have been expecting you".