19. The Man Under the Hood

Complete story — includes the ending

Oliver's team destroys Isabel's lab so that Slade cannot use it to mass produce Mirakuru. In response, Slade steals an electronic Skeleton Key from Oliver's hideout. He uses it to get a bio-transfuser from the S.T.A.R. Labs facility where Caitlin Snow and Cisco Ramon work so he can transfer Mirakuru-infused blood to the freed convicts. Oliver tracks down Slade and discovers that he is using a kidnapped Roy as the blood donor. Oliver rescues Roy; in the process, Isabel, who is revealed to have been involved with Robert previously, is critically shot. Oliver states there is a cure for Mirakuru and Felicity enlists the help of Caitlin and Cisco. Slade's super soldiers gather and he uses his blood to both heal and empower Isabel. Meanwhile, Laurel discovers that Sara is the female vigilante. Laurel tries to tell Quentin about the Arrow's identity, but he dissuades her from telling anyone. Laurel later blackmails her supervisor into releasing and reinstating Quentin. Thea leaves home, even after Oliver tells her that Robert knew about her paternity. In flashbacks, Oliver kills Ivo on his request after Ivo tells him the location of the Mirakuru cure.