Oliver and Thea are concerned when a family friend plans to run for mayor. Thea starts to exhibit side effects from the Lazarus Pit. Felicity asks an employee for help with a business decision.

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

Brie Larvan breaks out of jail and turns up at Palmer Tech threatening to kill everyone unless she gets the bio-chip that is implanted in Felicity’s spine. When Oliver realizes that Felicity, Thea and Donna are trapped in Palmer Tech with everyone else, he looks to a surprising ally to help Team Arrow save the day.

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.