Police forensic scientist, Barry Allen, and his wife, Picture News reporter, Iris West, are attending a showing of the film, Gorgunta. Suddenly, the theater is attacked by a giant, synthetic horse. Allen, as the Flash, aids in evacuating the theater, before it collapses under the massive steed's assault. When the Flash closes in to confront the horse, the crowd is astonished at what happens next. In Coast City, the Green Lantern is alerted to the Flash's peril. The Green Lantern travels to Central City, and confronts the horse. His power beam construct, however, dissipates before it can strike the horse. The horse seizes control of the power ring energy, reshaping it into a cannon, that shoots the Green Lantern out of the sky.
The Flash races the Green Lantern out of the horse's path, before he can be trampled to death. The Flash re-engages the horse, only to have his super-speed attack turned back on him again. The Green Lantern tries an indirect attack, hurling a large boulder at the horse. The rock shatters on the horse's hide, but does manage to break the horse's collar off. Inspecting the collar, the two heroes learn the horse originated in the 25th century. Journeying 500 years into the future, the two heroes learn that the "Syntho-Steed" was created by Eobard Thawne. The Syntho-Steeds were created to replace the now extinct horse in racing events. Thawne, though, is the Flash's greatest nemesis, Professor Zoom, also known as the Reverse Flash.
For creating the Syntho-Steeds, Thawne has been pardoned for all of his crimes. Thawne agrees to go back in time to aid the Flash in defeating the rampaging Syntho-Steed, with one condition. The Green Lantern must steal the priceless Raxalus Wings sculpture, and deliver it to Thawne. Though it violates his oath, the Green Lantern agrees to the crime, then beams the two speedsters back to the present. Within moments, crowds of onlookers see the Raxalus Wings sculpture launch itself into the sky. The Green Lantern is seconds away from taking possession of the sculpture, when he is thwarted by the Green Lantern of that era. The Green Lantern sends a power beam around the world, to strike his future counterpart in the back.
The Green Lantern quickly regains the sculpture, only to become caught in a power ring constructed cloud. Bombarded with emerald lighting, the Green Lantern loses his grip on the sculpture. Seeding the cloud, the Green Lantern creates a torrential downpour, that momentarily incapacitates his foe. Grabbing the statue on the run, the Green Lantern flees, only to be disintegrated by the future Green Lantern. The Flash and Professor Zoom run down the Syntho-Steed. Again, their super-speed powered attack is turned against them. The Flash merges his molecules with Professor Zoom, joining them together. Their super-speed powers combined, the two speedsters are able to fell the Syntho-Steed.
Stomping on the Syntho-Steed at super-speed, the Flash and Professor Zoom generate enough heat to melt the Syntho-Steed down into slag. True to his word, the Green Lantern delivers the Raxalus Wings to Professor Zoom. The moment Professor Zoom takes possession of the statue, it disintegrates. As the Raxalus Wings were yellow, the one color the Green Lantern's ring cannot affect, the Green Lantern could not protect the sculpture from the ravages of time travel. Professor Zoom accidentally confesses to sending the Syntho-Steed back in time, as a scheme to force the Green Lantern to steal the Raxalus Wings sculpture for him. The Flash removes Professor Zoom's costume from him, depriving him of his super-speed powers.
Professor Zoom is returned to the authorities of the 25th Century. Green Lantern reveals that he set his ring to return him to the present, the moment he was struck by his future counterpart's ring beam, thus escaping his seeming fate.