The Flash is planning something particularly mind-blowing for the spring run.

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The cast of The CW drama spent the better half of December working on episodes 13 and 14, and from the actors have to say, fans will be suitably impressed by the upcoming storyline.

"One more day of shooting before our cast & crew finally take a well deserved break," Grant Gustin (Barry) teased on Friday. "Halfway through 214, which will blow your minds. Truly."

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It is currently unclear what will go down during the untitled episode, but executive producer Greg Berlanti has hinted that it may be connected to episode 13.

"[Episodes 13 and 14 are] the two craziest episodes that we've ever done - and probably two of my favorite episodes ever," executive producer Greg Berlanti told TV Line. "There's incredible, incredible stuff."

Behind-the-scenes photos from various sources indicate that episode 13 will take place on Earth-2. Jay Garrick (Teddy Sears) was seen donning his Crimson Comet garb as he somehow harnessed the speed force to clear a hospital on Dec. 9, and an Earth-2 Barry was also spotted the same day. The most shocking reveal, however, came later that night when Gustin was seen filming with Danielle Panabaker's Killer Frost.

Find out exactly what's in store for the STAR Labs team when The Flash returns to The CW on Jan. 19. Click the video below to see a preview for "Potential Energy."