The CW has released an extended trailer for the Flash/Arrow crossover. You can check it out above and read a synopsis for both parts below.
“Legends of Today” — (8:00-9:01:00 p.m. ET) (Content Rating TBD) (HDTV)
PART ONE OF THE EPIC CROSSOVER WITH “ARROW” — In its second major crossover event with “Arrow,” Vandal Savage (guest star Casper Crump) arrives in Central City and sets his sights on Kendra Saunders (guest star Ciara Renée). After Vandal attacks Kendra and Cisco (Carlos Valdes), they turn to Barry (Grant Gustin) for help. Realizing how dangerous Vandal is, Barry takes Kendra to Star City and asks Oliver and team to hide her until he can figure out how to stop Vandal. However, things quickly go from bad to worse when a man with wings AKA Hawkman (guest star Falk Hentschel) shows up and flies off with Kendra. Meanwhile, Harrison (Tom Cavanagh) develops a serum to make Barry run faster and asks Jay (guest star Teddy Sears) to test it out. Ralph Hemecker directed the episode with story by Greg Berlanti & Andrew Kreisberg and teleplay by Aaron Helbing & Todd Helbing (#208). Original airdate 12/1/2015.
“Legends of Yesterday” — (8:00-9:01:59 p.m. ET) (TV-PG, V) (HDTV)
PART TWO OF THE EPIC CROSSOVER WITH “THE FLASH” — Oliver (Stephen Amell) and Barry Allen (guest star Grant Gustin) take Kendra Saunders (guest star Ciara Renée) and Carter Hall (guest star Falk Henstchel) to a remote location to keep them hidden from Vandal Savage (guest star Casper Crump) while they figure out how to defeat him. Malcolm (John Barrowman) arranges a meeting between Vandal, Green Arrow and The Flash that doesn’t go as planned. Meanwhile, Felicity (Emily Bett Rickards), Thea (Willa Holland), Diggle (David Ramsey) and Laurel (Katie Cassidy) work with Team Flash to come up with a weapon powerful enough to destroy Vandal Savage. Thor Freudenthal directed the episode with story by Greg Berlanti & Marc Guggenheim and teleplay by Brian Ford Sullivan & Marc Guggenheim (#408). Original airdate 12/2/2015.
