S2, E9: When Mark Mardon a.k.a. The Weather Wizard (recurring guest star Liam McIntyre) returns to break Leonard Snart a.k.a. Captain Cold and James Jesse a.k.a. The Trickster (recurring guest star Mark Hamill) out of Iron Heights, Barry must stop these rogues from taking over Central City during Christmas. Meanwhile, Joe and Iris meet Wally West (new series regular Keiynan Lonsdale).