'Arrow' Recap: Huge Revelations Are Made In "Star City Slayer"

With Team Arrow back together, crime doesn't stand a chance in Star City — right? As usual, full spoilers for "Star City Slayer" are up ahead. If you haven't watched tonight's episode of Arrow, proceed with caution. That said, here's what happened on tonight's episode of Arrow.

The threatening messages continue getting sent to Dinah, she even gets one on her desk at work. Not just that, Diggle gets one at ARGUS and Rene has another note left on the door to his apartment — the entire team is receiving death threats.

Team Arrow begins investigating the notes when they find out one of Ricardo Diaz's former acquaintances has also been killed and a similar note was left behind. Curtis does some research and finds out the attacker uses a rare drug used to immobilize victims and tracks down the only shipment of the drug in Star City to a run-down house in the Glades.

After the team investigates the house, they find evidence that the attacker used to be an inmate at Slabside. In the basement, Dinah uncovers the typewriter the attacker has been using for the notes, in addition to mementoes from the killings. As she's looking around, she's attacked from behind and her throat is slashed — we find out the attacker is Oliver's former prison cellmate, Stanley. Curtis runs downstairs and is able to cauterize her wound, saving her life.

The former inmate then goes to the Queen residence and fills the entire condo up with the stabilizing drug, freezing Oliver, Felicity, and William in their tracks as they eat dinner. There, Stanley appears completely unhinged and informs the trio he's the one killing everyone around town. When Stanley's distracted, Oliver's able to move enough to grab a glass bottle to break over Stanley's head.

At the end of the episode, we see a shot in the future — Blackstar/Mia is revealed as Mia Smoak, the daughter of Oliver and Felicity!

Other developments in this episode include:

• William reveals he was expelled because he punched a fellow student and proceeds to fight with his dad and Felicity. Later that night, Oliver tries speaking to him, but they're interrupted when William's maternal grandparents arrive and inform Oliver that William wants to live with them. After Stanley's attack, Oliver tries reconciling with William, but he still wants to go live with his grandparents in Central City.
• In the future, William, Roy, Dinah, and Zoe are trying to find Blackstar so that they can uncover where Felicity stored her stockpile of bombs. The group goes to check out the former Team Arrow bunker and they're all knocked out by tranquillizers shot by Blackstar and Connor Hawke. After they wake back up, Blackstar reveals to the team that Felicity isn't dead after all — she threatens the team harm if they don't provide her with the codes needed for Felicity's setup.
• Diggle offers Curtis a job to lead ARGUS' science division. Curtis turns down the job and takes another in Washington DC. It's heavily hinted that Curtis might be leaving the show.

What'd you think of "Star City Slayer?" Let us know your thoughts on tonight's episode of Arrow in the comments below!

New episodes of Arrow air Monday nights at 8 pm Eastern on The CW.