After the epic two-part special that pit Team Flash and Arrow against the immortal, Vandal Savage, it is time for both teams to concentrate on stopping the threats on their respective cities again.

Central City is in danger of being taken over by villains like the Weather Wizard, The Trickster and Captain Cold this holiday season and it is all up to Barry Allen if he can put a stop on their plans.

Here's a synopsis of the episode courtesy of Comic Book.

"MARK HAMILL, WENTWORTH MILLER AND LIAM MCINTYRE RETURN; KEIYNAN LONSDALE JOINS THE CAST AS WALLY WEST - When Mark Mardon AKA The Weather Wizard (guest star Liam McIntyre) returns to break Leonard Snart AKA Captain Cold (guest star Wentworth Miller) and James Jesse AKA The Trickster (guest star Mark Hamill) out of Iron Heights, Barry (Grant Gustin) must stop these rogues from taking over Central City during Christmas. Meanwhile, Joe (Jesse L. Martin) and Iris (Candice Patton) meet Wally West (Keiynan Lonsdale)."

Check out the spectacular teaser below.

It would be interesting to see how Joe and Iris will react when they go face to face with their long lost family member, Wally. Fans should be on the look-out for Keiynan Lonsdale as EP Andrew Kreisberg said that he is the perfect embodiment of the character in an interview with Deadline Hollywood months ago.

"Just like when we met [star] Grant [Gustin] for the first time, we instantly knew Keiynan embodied all the heart and courage of a hero," producer Andrew Kreisberg said. "We are so excited to be bringing this much-beloved character onto the show."

Are you thrilled to see Wally West team-up with Barry and the rest of the gang? Will he join the list of speedsters in this season as well? Stay tuned!