This has got to be one of the best Flash stories ever!
Cover Date: September 1961
In order to assist Iris West, Flash performs at a fundraiser in the Central City community center. During the performance Flash is using his super-speed powers to achieve amazing feats. During one such trick, of rope climbing, he disappears.
When Flash reappears, he is outside the city. As he heads back into town, he notices that it is not Central City at all. It is Keystone city, a fictional city from comic books, which serves as the home of Jay Garrick, the Golden-Age Flash.
Flash looks up Garrick in the phone book and arrives at his door as Barry Allen. Barry reveals his knowledge of Jay’s origin and history. He also reveals his secret identity to Jay. It seems that the two worlds occupy the same space but vibrate at different speeds. Things evolved slightly different on each Earth. Barry is aware of Jay from reading the comic books of his Earth, which were written from Gardner Fox’s dreams. Jay, who has been retired for over a decade, comes out of retirement, and together the two Flashes set out to solve a series of crimes that have struck Keystone City.
Garrick’s old foes the Fiddler, the Shade, and the Thinker have joined forces in an attempt to draw Flash out of retirement. The Flashes split up to look for the criminals responsible for the crimes. Jay encounters the Thinker, but he is outwitted by his old foe. Barry encounters the Shade, who is puzzled by Flash’s changed appearance. Shade is able to escape as well. When the two crooks meet up they compare notes and realize there are two Flashes.
The Fiddler is committing a third crime across town. Shade and Thinker arrive to warn their partner about the Flashes. They discover that Fiddler has already caught them using his musical spell. He forces the duo to steal jewels for him. When he is about to escape with his partners, he commands the Flashes to stay behind. The Flashes capture the villains anyway. They put the jewels in their ears which blocked Fiddler’s musical commands.
Barry and Jay part company, with Jay permanently out of retirement. Barry returns back to his own world.