Blood Debts

"Blood Debts" is the tenth episode of the fourth season of Arrow and the seventy-ninth episode overall.

Synopsis
Darkh's most recent attack leaves Felicity paralyzed in the hospital, and Oliver is seeking revenge, Oliver goes on a brutal manhunt looking for Dahrk, even going as far to temporarily freeing Lonnie Mason, plans go awry though when Mason kidnaps Darkh's family, and Oliver Co. step in to save them. Oliver comes face to face with Darkh and they engage until Darkh voluntarily backs off, threatening Oliver with a little more time since he saved his family. Meanwhile, Diggle finally gets Andy to talk and attempts to reconnect to him as his brother,

Production
Preparation ran from October 20 until October 30, 2015. Shooting ran from November 2 until November 10, 2015.