Police forensics scientist, Barry Allen, solves a classic "locked door" murder mystery. By chance, the murderer is struck down, by a hit-and-run driver. As he lies dying in the street, the murderer confesses to the crime. Allen's crime-solving brilliance is lauded by the local media. Allen's wife, Picture News reporter, Iris West, is somewhat surprised at Allen's sudden penchant for egotism. Unbeknownst to Allen, he has been exposed to a mutagenic radiation, by his arch-nemesis, the Trickster. Much to the Trickster's chagrin, the Flash has been keeping a low profile of late, while Allen hogs the spotlight from his costumed alter-ego.
The Trickster is desperate to be on hand when his radiation treatment slays the Flash. En route to a charity appearance at Central City's Grand Prix, Allen, as the Flash, takes time out to apprehend some jewel thieves. During his takedown of the crooks, the Flash begins experiencing terrible headaches. With the thieves unconscious, the Flash turns to face the crowd, only to see them recoil in horror from him. It is at that moment that the Flash notices that his cranium has expanded to freakish proportions. The Flash contacts his wife to explain the situation to her, then holes up in a laboratory, desperately seeking a cure for his condition.
His headaches become so great that the Flash bolts from the laboratory, to try to clear his head. When the Trickster finds the Flash, he immediately hits him with sneezing powder. Racing in tight circles on the surface of a lake, the Flash generates a waterspout, that brings the Trickster down to Earth. The Trickster retaliates with explosive peas. As the Trickster once more ascends to the sky, the Flash spins his arms about, like helicopter blades, and pursues his old foe. Ultimately, the Trickster gets the better of his nemesis, and carries his unconscious foe to his secret lair.
The Trickster takes credit for the Flash's horrifically swollen skull. Blowing up a "Flash" balloon, the Trickster demonstrates what will soon happen to the Flash, as his cranium continues to swell. The Flash, though, notices that, ever since the Trickster brought him to his lair, his headaches have stopped. The Flash lunges at the Trickster. A telescoping fist rams forth from the Trickster's chest, pinning the Flash against the wall. Jets of scalding hot water open up on the Flash's head. Vibrating at super-human speed, the Flash passes through the fist, then begins pelting the Trickster with dishes.
After bashing the Trickster with a recliner, the Flash pummels his foe into unconsciousness. The Flash realizes that residual radiation from the mutagen's antidote lingered on the mynah bird that the Trickster had experimented on. This residue was alleviating the Flash's headaches. Reverse engineering the antidote from the mynah bird, the Flash is able to restore his cranium to it's normal proportions. West writes the article on the Flash's latest adventure, while the Trickster punishes himself, for his failure, behind bars.