The team faces off against a formidable villain nicknamed The Calculator. Meanwhile, Nyssa makes her move and Roy Harper returns to Star City.

Oliver receives an offer from Nyssa that is hard to refuse. Meanwhile, Thea continues to battle the blood lust, Malcolm steps in to help his daughter, and Laurel has a heart to heart talk with Nyssa.

When Team Arrow learns what Damien Darhk's next move is Felicity realizes she needs to ask her father, Noah Kuttler, for help. Noah and Oliver have a heart to heart talk that leaves Oliver rattled.

Following the shocking events in the previous episode, Oliver and Diggle race to rescue Thea, while Felicity, Curtis and Noah join together to stop Darhk.

Quentin Lance is kidnapped by Black Siren and Cayden James, who are looking to trade Lance’s life for a weapon of mass destruction. Oliver and Team Green Arrow must figure out a way to save Lance while still keeping the city safe.