The epi is titled "Running to Stand Still".
"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).
The Flash "Running to Stand Still” was directed by Kevin Tancharoen and written by Andrew Kreisberg. The episode airs Tuesday, December 8, at 8pm on The CW."
All-out war comes to next week's Winter Finale of #TheFlash! Catch up on the latest episode: https://t.co/SvUvUYYZ3f https://t.co/cgGH5jnUet— The Flash (@CW_TheFlash) December 3, 2015