Heroes have risen to fight villains throughout the millennia. Now, heroes attempt to defend the planet Oa from mind-controlled superheroes taken over by Starro. The heroes drive off the first wave, but watch as a vast entity approaches them.
Batman and Booster Gold return from the 31st century and arrive at the Batcave. They realize that there's been an increase in meteor strikes and a strange signal from Star City. Booster realizes that it's the third of the month, and remembers from his studies of the past that something huge happens to that day. Unfortunately, he doesn't remember exactly what, and makes a hasty exit. Batman continues his analysis but discovers that Faceless Hunter has arrived in the Batcave.
The villain informs Batman that the signal is a homing beacon to bring its master to Earth. Faceless Hunter attaches one of the Starro drones to Ace the Bathound, and Batman attempts to slow the alien down. When his own weapons don't work, Batman uses his collection of rogue weaponry without success. Next he uses a remote control to send his robot dinosaur after Faceless Hunter. It quickly defeats the robot ad follows Batman into the garage. Batman opens fire with weaponry from the Batmobile but Faceless Hunter is unaffected. He grabs Batman and prepares to attach a Starro, but Booster returns to tell Batman there's an invasion on that day in history. He opens fire with his blasters, narrowly avoiding possession. Faceless Hunter teleports away, and warns them that Earth has already fallen.
Across the planet, mind-controlled heroes attach Starros to the civilians. Batman and Booster Gold watch the gathering horde of people falling under the aliens' control. The heroes watch from a rooftop and realize they need an army of superheroes. Batman sends a signal to all unaffected heroes and makes contact with Captain Marvel, B'wana Beast, and Firestorm. Booster Gold is unimpressed and Batman admits that they may not be much, but they are Earth's only hope for survival. B'wana Beast demonstrated his power for Booster Gold, merging a rat and a pigeon. Batman informs them that they have to disable the signal before the primary Starro arrives.
The heroes arrive at Star City but find the controlled heroes waiting for them. Batman gets to the signal device but the Atom thwarts his efforts to destroy it. The other heroes are soon outnumbered, and B'wana Beast comes face-to-face with Vixen, his fianceé.
Batman defeats Atom, but an image of Faceless Hunter appears to inform him that he's too late. The alien destroys the transmitter device and watches from space as B'wana Beast merges animals to aid him. Batman orders his teammates to retreat and they slip away via the sewers.
The heroes go to STAR Labs and Batman analyzes the captive Vixen. He realizes that the Starro drones are absorbing energy and passing it onto their master. Before they can remove it, the possessed Vixen gains consciousness. Starro speaks through her, informing them that it has conquered thousands of planets for millennia, and will soon be there.
After Vixen passes out, Batman and his team go to the roof and watch the giant Starro descends from the sky. They launch an attack but Starro is too powerful for them, and Faceless Hunter arrives to attack Batman and B'wana Beast directly. Starro smashes Captain Marvel, Firestorm, and Booster Gold down through the street and then starts feeding.
The trio below avoids damage when Firestorm transforms the street into foam rubber. They then change to their civilian identities to blend into the crowd. Above, Faceless Hunter continues his assault on Batman and B'wana Beast, and explains that he agreed to serve as Starro's herald in return for the safety of his people. He ignores their suggestion that they ally together and opens fire.
Booster Gold and the others get some of the unaffected humans to safety, but Starro seems them and starts draining the heroes' energies. They change to their heroic identities but Billy Batson is taken over before he can say his magic word.
As Faceless Hunter continues his attack, B'wana Beast merges a bird and a caterpillar and tries to cocoon Faceless Hunter without his success. The alien admits that he finds B'wana Beast intriguing, much to the hero's surprise.
Firestorm realizes that there's a limit to the power the drones can hold, and overloads the drone on Billy's face. When he says the magic word, the magic lightning hits Starro and Firestorm realizes how to defeat it. Billy says "Shazam!" repeatedly and Starro is overwhelmed, crashing to the ground.
Faceless Hunter realizes his master has been defeated, but informs Batman that he has a new weapon. He knocks out the Caped Crusader and grabs B'wana Beast, and then teleports away.