Oliver learns that the DA has another witness against him--Roy Harper. Team Arrow set out to find Roy and learn if someone is coercing him to testify. Meanwhile, Black Siren passes herself off as Laurel and claims that she's been in captivity for two years.

Oliver realizes that Diaz has subverted Hill and Armand, and faces a challenge from within what remains of the team. Meanwhile, Curtis discovers that his new boyfriend dislikes vigilantes.