"The Plague That Struck the Justice League!"
When Batman, Flash, Green Lantern, and the Atom suddenly find themselves grown to gigantic size, they are contacted by an alien named Dr. Benderoin, who tells them that they have been infected with a virus that will kill in 10 hours and that anyone they have been in contact with have been infected as well. Benderoin tells them that it is due to their exposure to the Unimaginable. The League calls in their stand-by member Metamorpho for help but Benderoin insists that he cannot cure the other heroes this time as his atoms exhausted their therapeutic value when they cured Metamorpho himself.
After fighting a number of off world threats, and then stopping an aurora borealis on Earth that empowers criminals on Earth with super powers, Batman deduces that Blenderoin is really the Unimaginable in disguise, who has been stripped of his powers and was using the JLA to gain the means to restore his abilities. In realizing the truth, the Unimaginable is easily defeated by Superman. Afterwards, Batman and the others are restored to normal.