Arrow delivered an action packed mid season finale with “What We Leave Behind.†Prometheus is ready to take down Team Arrow once and for all. Felicity is finally ready to introduce Billy to her friends. And Oliver remembers something from his past that could help them find and stop Prometheus.
At the Mayor’s annual holiday party, Felicity is finally ready to introduce her boyfriend, Detective Billy Malone, to her friends. She has a few too many cocktails to help the nerves but ends up ruining Curtis’s cover story for the late nights with his husband, Paul. When Paul goes to leave the party, Curtis runs after him and runs right into Prometheus. Curtis is attacked but thankfully will be okay. His relationship with Paul, on the other hand, won’t be so lucky.
Paul now realizes that his husband has been lying to him this whole time. Curtis comes clean and tells Paul that he has been working with the Green Arrow. Paul is not okay with knowing that his husband might not come home every night. He tells Curtis to pick either his marriage or being a vigilante. Curtis knows that he can’t stop being Mr. Terrific, so is his marriage coming to an end? Paul knows how happy Curtis has been and decides to make the decision for him. Paul leaves, but how will Curtis handle this new life without someone to come home to?

In the flashback this episode, we only flash back a few years. Oliver is a killer vigilante as the hood, and Diggle is the only one who knows his secret. Original Team Arrow hasn’t even been formed. Oliver remembers going after a man named Justin Claybourne. Claybourne was responsible for an outbreak where his drugs actually cure the disease. He profited by creating the demand for his product then jacking up the price of the drug. The hood eventually killed Claybourne, but it seems that Prometheus is out for revenge of Claybourne’s death. So if it’s not Justin Claybourne, who is Prometheus?
Felicity tries to keep her boyfriend away from the Prometheus investigation, but Billy is a cop and won’t just stand by. After Prometheus lures Team Arrow to the old Claybourne factory and Evelyn is outed as a traitor, Billy goes to find any evidence he can. He finds a baby photo in an old lock box and sends it straight to Felicity. With a little bit of digging, Felicity finds out that Justin Claybourne had a child, who is more than likely exacting his revenge on the Green Arrow for killing his father.

Oliver feels responsible for creating Prometheus from his hood days when he killed without thinking of the consequences. Once he figures out where Prometheus is going to be, Oliver goes on his own. Prometheus knows that Oliver is there to kill him and ends up tricking Oliver instead. After thinking he has killed Prometheus once and for all, Oliver notices something strange, a weapon taped into Prometheus’s hand. It turns out that Prometheus put Billy inside of his suit and posed him just for Oliver to kill.
I can’t help but wonder if Oliver hadn’t gone alone, they could have all captured Prometheus together rather than just shooting to kill. Thankfully, the rest of the team, including Felicity, understands that Prometheus is the real person to blame in all of this. What Prometheus thought would tear the team apart is actually going to bring them together.
We end the episode with a couple of interesting and highly confusing scenes. Oliver goes to see Susan Williams. She offers him some vodka that is clearly Russian. Oliver mentioned that the same Russian woman who trained him once upon a time must have trained Prometheus. Does Susan have something to do with Prometheus? When Oliver goes back to the Arrow cave, a familiar face shows up… Laurel Lance. How is this possible? Flashpoint seems to be the only logical explanation, but we will just have to wait for the answer.