The growing tension between Oliver and Diggle puts both their lives at risk when they go after Damien Darhk and a H.I.V.E. deployed meta-human. Meanwhile, Laurel talks Thea into returning to Nanda Parbat to ask her father to put Sara into the Lazarus Pit. However, Laurel is surprised when Nyssa refuses to do it.
Laurel must deal with the repercussions of taking Sara to Nanda Parbat. Meanwhile, Oliver asks Captain Lance for a favor and while he's not surprised at the response, he is surprised at what he finds out next.
Oliver and Barry hide Kendra and Carter in a remote location while they try to figure out how to defeat Vandal Savage; Felicity, Thea, Diggle and Laurel work to come up with a weapon to destroy Vandal.
An agent of Shadowspire who was an enemy from Diggle and Andy's wartime past shows up to Star City. Diggle must learn to trust Andy but he got more than he wanted about their shared time from war. Oliver however must learn a new way of life when Felicity is now in a wheelchair and receives her codename.
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.
As Oliver and Felicity look for a magical solution to defeat Darhk, a vengeance-driven Diggle gets a lead on Andy's whereabouts and heads off to confront his brother. Meanwhile, Alex takes Thea on a vacation that quickly turns into a nightmare.