Col. Steve Trevor advises the President of the United States to remain in his secure location in order to avoid infection by the Amazo Virus, which is, as far as he can tell, airborne and able to survive that way indefinitely. Currently, Superman, Batman, Wonder Woman and Lex Luthor are searching for patient zero, in the hopes that he might be the key to finding a cure. If they fail, though, billions will die.
Unfortunately, Batman has been infected, and is entering stage two of the infection – the transformation into a metahuman. Though this means he will develop super-powers briefly, the third stage is his inevitable death. He uses his powers to bring down patient zero, but begins to collapse. Superman catches him, and he admits that his power appears to be an amplified form of echolocation – like that of a bat. The meta-manifestation must therefore be somehow subconscious or psychologically based. As his condition deteriorates, Batman warns that Luthor cannot be trusted. The virus is filling his mind with a voice. Worriedly, Superman and Wonder Woman take Batman and patient zero back to Luthor in the hopes that he can develop a cure and save Bruce.
Meanwhile, just outside Metropolis, Luthor has been attacked by an assassin called Bullet, who is surprised to find that his kill-shot was deflected by a heavy layer of ice. Captain Cold held true to his position as head of security by saving Luthor’s life. Despite Steve Trevor’s attempts to prevent him, Cold freezes Bullet solid and tends to Luthor. Recovering, Luthor angrily marches over to Neutron, to force him to talk, despite the fact that being removed from his forced coma will cause him severe pain. Lex’s sister Lena begs him not to wake him, but Lex insists, throwing her out of the room.
When Neutron wakes, Lex gives him a brief explanation of who and where he is, adding that the Amazo Virus has removed Neutron’s ability to absorb and redirect radiation – meaning that he is now suffering from radiation poisoning and cancers. Lex leans in, warning that Neutron will die soon unless he saves him. And he won’t save him unless he is told who wants him dead. At that moment, he is interrupted by Superman and Wonder Woman with Batman and patient zero. Weakly, Neutron begs Luthor not to let him die, and he promises to get to work.
Soon, though, the victims of the virus begin whispering the word “us” over and over. Desperately, Luthor tests patient zero’s blood and realises that he can’t use it to develop a cure. He is just as sick as everyone else. He will need a sample of Superman’s blood instead. Confused, Superman wonders why, and Lex admits that he had infected Superman with the Amazo Virus four years ago. He had created it to leave Superman powerless, but it hadn’t worked, so he’d shelved it. Somehow, Superman’s body had fought it off, and if he has the antibodies, he is the key to curing the virus.
Superman grows enraged, but Lex insists that he had no intention of letting the virus get out like this. He’d meant it to work against Kryptonians exclusively. Superman doesn’t believe him, but Wonder Woman reminds that they don’t have a choice but to accept his help. Lex promises to help – in exchange for immunity.
Unexpectedly, though, they are all blasted through the wall by Batman’s metahuman ability, and when he begins speaking with a voice that his not his own, Lex admits that he had been afraid this would happen. The infected Leaguer members rise from their beds, and speak in one voice, warning that humans are wrong to think they are the dominant species.