|Season 4, Episode 11|
|H.I.V.E.||A League Of Their Own|
Ab Initio is the eleventh episode of Arrow Season 4 and the 80th episode overall.
BIRTH OF THE PHANTASM- Having captured Andrea, Oliver tries to reason with the young woman and dissuade her from her path of vengeance only to sympathize with Andrea's tragic backstory. Malcolm receives an ultimatum. Diggle defends the people of Corto Maltese against the remaining H.I.V.E. agents and is unexpectedly rewarded. Nyssa and Oliver butt heads on how to proceed with Andrea while Laurel takes a day to spend with a disturbingly serene Sara. When Sara's behavior takes a drastic turn for the worse, Nyssa takes her to the Glades, but Sara begins terrorizing the district. With Team Arrow and Nyssa on opposing sides concerning how to handle the quickly unraveling assassin, Laurel must decide who to trust with her sister's wellbeing. Oliver takes a big step to becoming who he wants to be.
- Stephen Amell as Oliver Queen
- Katie Cassidy as Laurel Lance
- David Ramsey as John Diggle
- Willa Holland as Thea Queen (credit only)
- Katrina Law as Nyssa al Ghul
- Caity Lotz as Sara Lance
- Colin Donnell as Tommy Merlyn
- Audrey Marie Anderson as Lyla Diggle
- Deborah Ann Woll as Andrea Beaumont
- Bex Taylor-Klaus as Cindy
- and John Barrowman as Malcolm Merlyn/Ra's al Ghul
Special Appearance ByEdit
- David Morrissey as Julian Mercer (flashbacks)
- Antagonist: Damien Darhk
- The episode's title is Latin for "In the beginning".
- Thea does not appear in this episode.