'The Flash' Season 2 Spoilers: Episode 9 Synopsis Released; What Will Happen In 'Running To Stand Still'?

Everything was new for Barry (Grant Gustin) in episode 8 of "The Flash" Season 2 as a mystical, new (immortal) villain brought the superhero to Starling City to call on the Green Arrow (Oliver Queen) for backup. While he and Oliver Queen may still have some business to take care of on "Arrow" Wednesday, the next episode of "The Flash," "Running to Stand Still," will be a return to normal (of sorts) as Barry faces an enemy from the past.

According to the synopsis for episode 9, the Weather Wizard (Liam McIntyre) returns to Central City on Christmas to break Captain Cold (Wentworth Miller) and the Trickster (guest star Mark Hamill) out of Iron Heights prison. Barry must try to stop him and the other rogues from taking control of the city and ruining everyone's holiday. On top of that, Barry still has Zoom (Tony Todd) to worry about. Dr. Wells (Tom Cavanagh) and Caitlin (Danielle Panabaker) synthesized a speed-enhancing serum in episode 8. Will they put to use in episode 9?

The synopsis for the new episode also reveals that Joe (Jesse Martin) and Iris (Candice Patton) are finally meeting Wally West (Keiynan Lonsdale)! Comic book fans will know Wally as the nephew of Iris West. In the comics, Wally is a Flash superfan and comes to visit his aunt in Central City. Then, a lightning strike results in him gaining the same powers as Barry and becoming Kid Flash. The show has tweaked things a bit, making Wally Iris' long, lost brother, instead of a nephew, and time will tell when he will meet his speedster destiny.

In the meantime, the crossover fun continues on "Arrow" as Barry and Oliver continue their fight with Vandal Savage (Casper Crump) and sort out the whole Hawkman/Hawkgirl problem. Considering Tuesday's "Arrow"-heavy cliffhanger, fans of "The Flash" will probably want to tune in to avoid missing anything important. Part 2 of the crossover event airs Wednesday at 8 p.m. EST on the CW.

Watch the promo for the "Arrow" crossover episode below:

Will Barry stop the Weather Wizard from breaking out Captain Cold? How will Iris react to meeting her brother? Fans will have to wait to find out. "The Flash" airs Tuesdays at 8 p.m. EST on the CW.