Police Forensics Scientist, Barry Allen, and his fiancee, Picture News reporter Iris West, present her niece, Inez, with a rocking horse. As Inez prepares to mount the rocking horse, it launches itself into the sky. Allen pursues the rocking horse, and spies the Trickster closing on it. The Trickster mounts the rocking horse, and proceeds onward to a floating art gallery, housed in a dirigible. Allen, as the Flash, generates a tornado, that he then rides up to the dirigible. The Trickster emerges, his saddle bags filled with rare canvases. To distract the Flash from capturing him, the Trickster destroys the dirigible, endangering the lives of the art patrons trapped inside the cabin.
By the time the Flash has safely lowered the cabin to the ground, on a super-speed generated cushion of compressed air, the Trickster has made good his escape. The Flash, as Allen, revisits the toy store where he purchased the rocking horse. There, Allen learns that the Trickster made two other purchases, which means two more crimes are in the offing. The first of these crimes occurs at sea, where the Trickster, riding a jet-powered surfboard, robs a luxury liner. To distract the Flash from capturing him, the Trickster uses his jets to kick up an enormous tidal wave. The Flash evacuates the liner, carrying all of it's passengers to shore, before the wave capsizes the vessel.
Once again, though, the Trickster has made good his escape. The Flash, as Allen, spends the next day in his laboratory, preparing for his next encounter with the Trickster. Alerted by police bulletin that the Trickster has just robbed a bank, Allen, as the Flash, races after his foe. With dollar bills trailing behind him, the Trickster flees on a motorized tricycle. As the Flash closes on the Trickster, he finds himself being repelled backwards. Undeterred, the Flash hurls magnetized thumb tacks at the the Trickster's tricycle, immobilizing it. Tearing off the tricycle's horn, the Trickster uses it to envelop the Flash in a smoke screen.
The Flash easily disperses the noxious cloud, by waving his arms at super-speed. The Trickster then ensnares the Flash with the rubber of the tricycle's wheels, but again the Flash is able to quickly free himself. The Trickster reveals that the tricycle's handlebars fire armor-piercing needles. The Flash dodges the Tricksters assault, retaliating with a barrage of paper money planes, hurled at high velocity. Unwilling to destroy the money to defend himself, the Trickster hesitates, allowing the Flash to punch him into unconsciousness. Allen and West buy Inez a new rocking horse, but Inez is upset when she discovers that it doesn't fly.
Professor West is en route to Central City, to unveil his latest scientific invention. Absentmindedly, West shows up at the wrong address, a safe house for Communist spies. Playing along with West's misperception, the spies allow him to demonstrate his latest discovery, the protocon ray. Bathing a bowl of grapes with protocon radiation, West causes the grapes to grow to colossal proportions. Immediately seeing the obvious use for such a device, the spies abduct West. Searching for the missing scientist, the Flash tracks West down, at the Communist safe house. The Flash is seconds away from taking down the spies, when one of the enormous grapes falls to the floor and explodes.
Though able to vibrate fast enough to cause most of the the explosive force to pass harmlessly through him, the Flash is, nonetheless, knocked unconscious. The spies take the opportunity to flee, with West. Upon reviving, the Flash catches up with the spies, at sea. The spies hold the Flash at bay, by threatening to murder West. The absentminded professor surreptitiously activates the protocon ray, enlarging a bowl of fruit. That brief moment's distraction is all the Flash needs to beat down the entire spy ring. The Flash escorts West to the Science Conference. Sadly, the absentminded West can no longer remember how to activate the protocon ray.