Police forensics scientist, Barry Allen, and his wife, Picture News reporter, Iris West, are on their second honeymoon. Though Allen has agreed to leave his Flash identity behind, while they're away, a sudden blowout forces him into super-speed action. Allen manages to exit the car, remove the blown tire, replace it with the spare tire, and return to the car, all without West ever noticing that he moved at all. Allen veers off the main highway onto a dirt road. West is puzzled until Allen arrives at the Hideaway Hotel. Though the Allens made no reservations, the front clerk seems to have been expecting them. The Allens are told to wear their pendents at all times, the same as the other guests.
In their hotel room, Allen confesses that he knew nothing at all about the hotel, but suddenly felt compelled to drive there. Realizing they've inadvertently taken the place of another couple, Allen, as the Flash, heads out to look for them. The Flash finds the other couple's car, at the bottom of a rockslide. Digging them out, the Flash confirms that the other couple has, in fact, died. The Flash removes their pendents, then sequesters their bodies in a nearby cave. Back at the hotel, the Flash, as Allen, realizes that he must have picked up the same homing signal the pendents receive, when he was moving at super-human speed to change the tire.
Their pendents suddenly begin glowing brighter than normal, prompting the Allens to join the other guests in an underground chamber, beneath the hotel. There, they are addressed by a strangely garbed man, who outlines a horrific plan to shift the Earth in dimensional space, with another planet, so that the Earth is enveloped in a comet's tail. Allen realizes that the other guests at the hotel are all aliens. These aliens have occupied the Earth for over a year, monitoring Cosmictron Power Rods, which will shift the Earth in dimensional space with their own planet, when the comet passes through their space again.
The briefing is interrupted when the couple the Allens replaced enter the room, clearly still alive. The aliens de-activate the illuso-aura, provided by the pendents, revealing themselves as aliens, and exposing the Allens as terrestrials. Allen races West out of the chamber, donning his Flash costume as he goes. Four blaster pistols pursue them. The Flash draws the guns off, engaging in evasive maneuvers. Ultimately, the Flash aligns the guns into a crossfire, that he evades, causing the guns to fire on one another. The Flash's super-speed vibrations upset the delicate balance of the aliens' Power Flux Wheel generators, leaving them without enough power to activate the dimensional shift.
The Flash learns the aliens purpose is actually beneficial to the Earth. When their planet was exposed to the comet's tail, it completely immunized their populace against all lethal microbes. The aliens merely wished to share their good fortune with another world. The Flash races along, inside the Power Flux Wheel, generating more than enough power to shift Earth into the alien dimension. The Earth is caught in the comet's trail, then shifts back to it's rightful location. The aliens return to their world, while the Allens resume their second honeymoon.
Camp counseler, Wally West, is out in the woods, with a group of young boys, to watch the meteor shower. One of the shooting stars fails to burn up in the atmosphere, revealing itself to be an alien craft, that lands in the camp. West, and the children are hit with a blinding flash, as the alien exits it's craft. The light momentarily paralyzes the boys, allowing West to go into action, as Kid Flash. Kid Flash charges the alien, only to be hurled back into the lake, by a protective force field. Kid Flash switches tactics, running around the alien, surrounding it in a field of densely, compressed air.
The alien is, again, unfazed. One of the children suddenly mutates into a horrific brute. Kid Flash is violently seized by the monstrous youth and thrown into the alien's view screen. Kid Flash manages to generate an air cushion, at super-speed, to soften his impact with the screen. A chipmunk also mutates into a gigantic horror, and chases after two of the children. Kid Flash attacks the woodland monstrosity, then cages it in a pen made of trees. Two more boys transform into gruesome monsters. Moving at super-speed, Kid Flash sees the radiation wave responsible for the terrifying transformations.
To avoid the wave, Kid Flash dives into the lake. The radiation purifies the previously polluted lake. Kid Flash sees an image of himself, as West, and the children, appear on the screen. Kid Flash realizes that the alien is merely a harmless tourist, who came to Earth to take pictures. The radiation given off during the developing process temporarily mutated the children, and the woodchuck. As the alien departs, Kid Flash invites the children to go swimming in the newly cleansed lake.