Ř4, D9: In part two of the epic crossover event with The Flash, Oliver and Barry Allen (guest star Grant Gustin) take Kendra Saunders (guest star Ciara Renée) and Carter Hall (guest star Falk Henstschel) to a remote location to keep them hidden from Vandal Savage (guest star Casper Crump) while they figure out how to defeat him. Malcolm arranges a meeting between Vandal, the Green Arrow and The Flash that doesn't go as planned. Meanwhile, Felicity, Thea, Diggle and Laurel work with Team Flash to come up with a weapon powerful enough to destroy Vandal Savage.