Flash of Two Worlds

"Flash of Two Worlds" is the upcoming second episode of the second season of The Flash.

Synopsis
Jay Garrick, a mysterious man from Earth-2, appears at S.T.A.R. Labs with a dire warning about an evil speedster named Zoom, who is set on destroying The Flash. Barry and the team must decide if they can trust this stranger even as they face yet another powerful meta-human. Meanwhile, Joe must deal with a determined officer named Patty Spivot who wants to join his meta-human task force.

Trivia

 * The episode is named after the iconic story of the same name published in September of 1961, featuring a crossover between the Barry Allen and Jay Garrick iterations of The Flash.
 * Sand Demon (a meta-human from Jay Garrick's world) and Zoom will appear in this episode