Iris West hosts a function at the Central City Community Center on behalf of the Picture News Orphan Fund Group. Unfortunately, the magician she had hired to entertain the children has failed to arrive. When Barry Allen shows up, Iris tells him the news and he says that he might be able to convince the Flash to stand in for the missing magician. Barry goes outside to change into Flash then races back into the center much to the delight of dozens of young orphans. Flash spends the next hour entertaining the kids with a variety of super-speed tricks. First, he astounds them by playing a game of tennis with himself. He serves the ball then races to the other side of the net to receive it just as the ball reaches its destination. He then does a variation of the old Indian rope trick. By vibrating his hands at super-speed, he makes a length of rope appear to rise into the air. He then begins scaling the rope while it continues to hover. As the children applaud, the Flash suddenly disappears. Iris wonders what could have happened to him.
The Flash reappears outside the city limits of a strange looking town. He has no idea where he is, but as he begins investigating the town, he realizes that he is no longer in Central City. He stops at a newsstand and picks up a copy of the Keystone City Herald. The Flash recognizes Keystone City as the fictional home town of his childhood comic book hero Jay Garrick – the original Flash. Barry recalls that comic book writer Gardner Fox created stories of Jay Garrick for Flash Comics based on dreams that he had experienced. He deduces that he must have vibrated between the dimensional barrier separating parallel worlds and has arrived on an Earth similar to the one that he had just left, except on this Earth, the Golden Age Flash was an actual living super-hero. Flash looks up Garrick's home address in a phone book, then races off to meet him.
The Flash arrives at the Garrick residence and meets an older Jay Garrick and his wife Joan. He tells them about he knows of Jay's secret identity as well as the fact that he is the Flash of an alternate universe. Jay tells Barry that he was thinking of coming out of retirement due to a series of strange crimes that have been plaguing Keystone City as of late. At the Keystone City Bank for example, a teller was shocked when money suddenly began floating out of her drawer. He further describes a robbery at Carmody's Jewel Salon where the crime was obscured by a thick cloud of pure darkness. Another mysterious theft involved an armored car that was ruptured by the sounds of strange music. Upon hearing this, Barry Allen offers to help Jay solve these mysterious crimes.
Across town, three super-criminals gather together and boast about the success of their most recent schemes. The Thinker commits crimes by way of a hypnotic Thinking Cap. The Fiddler is able to generate destructive sound waves with his violin and the Shade uses a special cane to create blankets of darkness to conceal his actions. The one thing these three have in common is that they are all old foes of the Flash. Each of them goes off to commit their next robbery.
The Thinker goes to the Jarvis estate and uses his Thinking Cap to order the guard dogs to warn the Flash about his actions should he arrive. He then hypnotizes Mister Jarvis's butler into relinquishing the valuable Neptune Cup to him. Jay Garrick arrives and is shocked when the dogs tell him that the Thinker is robbing the Neptune Cup. Jay speeds around the inside of the house, but he is unable to lay his hands on the Thinker. The Thinker is using his Thinking Cap to make himself appear to be in several places at once. When Jay finds the real Thinker he speeds after him, but the Thinker erects a wall of pure psychic energy that renders Jay unconscious upon impact.
Barry Allen meanwhile scours the docks when he sees a yacht off in the river with thick clouds of black smoke emanating from it. He runs off to investigate, but falls victim to the Shade. The Shade thinks that this Flash is Jay Garrick in a different costume. The Shade escapes in a speedboat, and lays down a slick trail of oil that prevents Barry from chasing after him. Barry later meets up with Jay at the Jarvis estate and Garrick tells him about the Thinker.
In the middle of town, the Fiddler rides down the street in his Fiddle Car and plays music from his violin. The sound waves shatter windows and cause a girder to fall from the top of a partially constructed skyscraper. A worker falls in the path of the girder, but fortunately, the Flashes arrive to save him. Jay pulls the man out of the way, while Barry deflects the falling girder. The Fiddler escapes during the melee and meets up with the Thinker and the Shade. Together they decide to rob the Keystone City Museum.
The Flashes track the villains down, but the Fiddler uses his violin to hypnotize them into obeying his commands. For fun, he has them dance for him like puppets on a string. Then he has them steal jewels for him. As the crooks gather their bounty, they prepare to leave, but the Flashes spring into action and apprehend them. The Fiddler doesn't understand how they resisted his mental commands. Jay explains that while they were forced to do the Fiddler's bidding, there was no command that prevented them from trying to escape. While robbing jewels for them, they plugged their ears with small gems, which distorted the effects of the Fiddler's violin, ultimately enabling them to break free of his control.
After the crooks are arrested, Barry and Jay say goodbye to one another and Barry invites Jay to visit his Earth some time. He then vibrates at super-speed and returns to his proper world. He then visits Iris at Picture News and explains to her why he disappeared.