Dinah, Diggle, and Rene continue to receive threatening notes for multiple days. The note maker has a board filled with pictures and news clippings of all the Team Arrow members.
Diggle gets some intel from Curtis about Dante. After briefing him, Curtis tells Diggle that he got a job offer in D.C. where he can actually help people. Diggle tries to convince him that they are doing good at ARGUS but Curtis is having a difficult time believing that.
Dinah helps train Zoe in self-defense. Later, Rene and Dinah talk about her concerns now that everyone in Star City knows she's the Canary. Rene assures it'll be okay. Rene shows her the threatening notes he's been getting and Dinah tells him she and Laurel have gotten them too.
The serial killer injects Kullens with something that paralyzes him and slices his throat open. The following morning, Team Arrow collects the clues they have about the Star City Slayer. Curtis and Oliver are the only two that haven't received a note yet.
Kullen's autopsy report reminds Dinah of a serial killer she heard about in Central City and calls Captain Singh to get some more intel.
Diggle tells Curtis he and ARGUS want him to be the head of their science and tech division so he can stay here in Star City.
Curtis does some research and finds out that the victims of the Star City Slayer have been drugged by mivacurium, causing them to be temporarily paralyzed. Curtis managed to track the one shipment in Star City to a condemned house in the Glades.
At the house, Diggle, Dinah, Curtis, and Rene split up. Rene and Curtis find a Slabside jumpsuit in a drawer and Dinah finds the killers obsession board and his a binder that shows his obsession with Oliver. She turns around and Stanley slashes her throat before running away.
The team finds her in time and Curtis uses a prototype he's been working on to save her. Dinah manages to point to the binder as she slowly recovers.
Oliver and Felicity question William about his expulsion. He tells them he got into a fight. When Oliver asks him why William lashes out and says Oliver never asks anybody how they feel like when he went to prison without discussing it with anyone first. Oliver tries to reprimand him but William just walks out.
Felicity and William have some fun playing with a Rubik's cube before Oliver comes home. Oliver attempts to have a heart-to-heart with William about coming back home permanently until they are interrupted by William's grandparents.
They tell Oliver that they are going to take William away from Oliver and all the danger that surrounds him. After they leave, Oliver tells William he can't be calling them for backup every time he's mad at him. William yells at his dad and tells him he wants a normal life and wants to live with his grandparents.
Felicity talks to Oliver and tries to get him to see where William is coming from. She reminds him that Oliver has the opportunity to provide William with a chance at normalcy he so desperately wants.
While eating dinner, Oliver, Felicity, and William become immobilized and Stanley walks into their home.
Stanley assures them that he doesn't want to hurt them, he just wants to talk. He says he had to warn Oliver about the people who he thinks are his friends. When Oliver calls him the Star City Slayer, Stanley lashes out but apologizes right away. He asks that Oliver just listen to him.
He swears he's been trying to protect Oliver from the people who are trying to hurt him and don't understand him like his team. He wants to form a new team with Oliver. He explains that the medicine he's given them was the same medicine his dad gave him so he was forced to listen and could be corrected.
He admits to killing both his parents and his brother after he tried to send him to Arkham Asylum. William manages to slide a glass bottle over to Oliver. Stanley begins to lash out again when Felicity calls him the Star City Slayer. Oliver knocks him out and smashes the bottle over his head.
The team reunites at the hospital where Dinah's recovering from surgery. Diggle found out Stanley's done this three times before.
Curtis tells Diggle he has to take the job in D.C. and also tells Felicity. He gives Felicity full control of Helix.
Oliver tells William that he will let him live with his grandparents if that's what he wants and William says it is for the time being. They say goodbye to him at home and assure him he has a home with them always.
Felicity gets a phone call from her doctor and tells her something that shocks her.
Zoe's having no luck with the Archer Program and Roy and William haven't had luck tracking Blackstar. William figures out that Felicity's been stockpiling the bombs and Roy has an idea where it could be. They arrive at the bunker but are quickly taken out with tranquilizer darts from Maya.
Maya tries to get Zoe or William to tell her what the access codes are for the Archer Program. When William accuses her of trying to blow up the city, she tells him that she isn't the person trying to do that and she isn't the person who killed Felicity.
Dinah and Roy ask Connor Hawk some questions about Blackstar but he stays quiet. Dinah figures out that he's Diggle's son.
William asks Maya who killed Felicity but she tells him that Felicity's still alive and that's why she needs Archer, so she can find her. She asks William what his connection to Felicity is and why he cares so much. He tells her that she's his stepmom. She asks if Oliver Queen is his father, but before he can answer, Dinah and Roy, escape and brawl with Maya and Connor.
Maya has a knife held to Dinah but William puts a gun to her head before she can do anything. She tells him he's not going to shoot her because her name is Mia Smoak, Felicity's daughter, and William's sister.