(Photo: DC Entertainment)

The CW has released the official synopsis for "Running to Stand Still," the Season Two midseason finale for The Flash, which features the return of Mark Hamill as The Trickster, along with fellow Rogues Captain Cold and the Weather Wizard.

...Oh, and a little someone called Wally West.

You can check it out below.

“Running to Stand Still” — (8:00-9:00 p.m. ET) (Content Rating TBD) (HDTV)

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). Kevin Tancharoen directed the episode written by Andrew Kreisberg (#209). Original airdate 12/8/2015.