Dark Waters

S4 E8: 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. After Vandal attacks Kendra and Cisco, they turn to Barry for help. Realizing how dangerous Vandal is, Barry takes Kendra to Star City and asks Oliver and the 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 develops a serum to make Barry run faster and asks Jay to test it out.