Season synopsis
Contains spoilers for this season and earlier seasons.
In the aftermath of the Undertaking, Oliver returns to Starling City determined to honor Tommy by abandoning lethal force. Sara Lance, long believed lost after the Queen’s Gambit sank, returns as the Canary and joins the fight; her return also strains Laurel’s recovery and the Lance family. Meanwhile, Sebastian Blood builds a political profile while secretly serving Slade Wilson, Oliver’s former island ally, who survived the Mirakuru serum and now seeks revenge for Shado’s death.
Slade turns Starling into a battlefield, using Mirakuru to create super-strong soldiers and recruiting Isabel Rochev and Blood. Team Arrow struggles to contain Roy Harper’s Mirakuru-induced violence while Diggle’s missions with A.R.G.U.S. bring the Suicide Squad into the story. Moira runs for mayor and reveals that she knows Oliver is the Arrow. When Slade captures Oliver, Moira and Thea, she offers herself to save her daughter; Slade kills Moira in front of her children, pushing Oliver toward the killing he had renounced.
Oliver and his allies survive Slade’s assault on the city. Felicity uses the cure developed with Caitlin Snow and Cisco Ramon to remove Slade’s Mirakuru, stripping away his enhanced strength; Oliver defeats him and leaves him alive in A.R.G.U.S. custody. The flashbacks reveal how Slade’s serum-fueled rage grew after he believed Oliver chose Sara over Shado. The season closes with Oliver’s team intact but permanently changed by Moira’s death, and with Thea leaving Starling alongside Malcolm, her biological father.