In "Unchained," the 12th episode of "Arrow" season four, Colton Haynes will reprise his role as Roy Harper, aka Aresenal. While Harper returns to Star City, Team Arrow will be in the thick of fighting The Calculator and Nyssa al Ghul will put a new plan in action.
ROY HARPER RETURNS; NYSSA MAKES HER MOVE -- The team faces off against a formidable villain nicknamed The Calculator (guest star Tom Amandes). Meanwhile, Nyssa (guest star Katrina Law) makes her move and Roy Harper (guest star Colton Haynes) returns to Star City. Kevin Fair directed the episode written by Speed Weed & Beth Schwartz (#412). Original airdate 2/3/2016.