Realizing Laurel (Katie Cassidy) has begun uncovering a past he has worked very hard to keep hidden, Brother Blood (Kevin Alejandro) kills the woman the world knows as his mentally-unstable aunt (Ana Mercedes), who is actually the mother who witnessed a young Blood kill his father in cold blood. Unable to get the Assistant District Attorney to risk investigating Starling City’s next mayor, Laurel turns to Green Arrow (Stephen Amell) for help.
Needing to stop the threat before Blood becomes a liability rather than an asset, Slade Wilson (Manu Bennett) gets Blood to remove the threat of Laurel by getting her arrested for her pill use. When the truth of her addiction comes out it makes even her father (Paul Blackthorne) doubt her story about Blood. Not prepared to let matters rest there, Brother Blood and his minions kidnap Laurel after she makes bail to draw out Green Arrow allowing for a little misdirection and arranging the death of an impostor which clears Sebastian in the eyes of both Laurel and Oliver.
Unable to come clean to Thea (Willa Holland) about his new strength and abilities, but needing to share his secret with someone, Roy (Colton Haynes) confides in Sin (Bex Taylor-Klaus) and decides to give his vigilante career another try (with Sin hitting the streets as bait for a lawyer who enjoys beating up local prostitutes). Unable to control his new strength and aggression, Roy puts the man in the hospital and would have done far worse if Sin hadn’t been there to stop him.
Roy’s increased aggression leads to beginning of a new partnership as Green Arrow offers to help train Roy to keep control of his actions and not let the serum control him. The episode also gives us our first look at Deathstroke in action, after fully mastering his gifts, as he doesn’t even break a sweat while taking out more of Blood’s disciples in payment for the politician’s recent mistakes and presenting a very real threat that even the combination of Oliver and Roy may not be able to stop. “Blind Spot” also includes more flashbacks to the island involving the fallout of Shado‘s (Celina Jade) death and Sara‘s (Caity Lotz) decision to stand-up to Ivo (Dylan Neal) and take back control of her life.