The recent episode of "Arrow", titled "Who are you" started with a follow-up of Laurel's reappearance.

Confronted by Ollie (Stephen Amell) on how she is pretty much alive(after seeing her die in front of him), Laurel (Katie Cassidy) gives some time travel excuse, saying that her sister Sara (Caity Lotz) brought her to the future to fix the embolism via the Waverider. When she became good as new, she was returned to be with her loved ones to Star City.

The team then has a party the following day, in honor of her return. According to TV Line, Felicity (Emily Bett Rickards) uses this to extract Laurel's DNA, which leads to a discovery that she could be an "evil twin" of Earth-1's Laurel, which she confirms by dropping her "pathetic pill" facade and sonic cries the place.

Earth-2 Laurel, aka Black Siren, splits the scene, which the team then finds out, through a S.T.A.R. Labs security cam, that she was uncaged by Prometheus, the current season's baddie.

Later on, she convinces Ollie to meet up on the Black Canary statue of all places, stating that she was only forced by Prometheus to do his bidding.

Though in doubt, he still goes to meet her, with the rest of the team close by. After a short fight ensues, breaking the statue in the process, Arrow knocks her out and is brought to their holding cell.

Behind bars, she shares her sad story, with Earth-2 Queen dying 10 years ago, which led her to make one bad decision after another. And while Ollie sees a chance at redemption, Felicity sees the ruse that is being played at him. Slipping nanites into Earth-2 Laurel, Felicity lets her escape so she can lead them to Prometheus. When the nanites go live, they were able to track Black Siren and a fight between the two parties followed. Green Arrow shoots Prometheus with a Diazepam arrow, which he easily fights off, claiming having tolerance against it.

Prometheus and Black Siren seem to have the battle planned out, according to Entertainment Weekly, as Black Siren threatens to end Felicity, Prometheus then asks Green Arrow to choose either her or him, with the hero going after the former. With the canary cry dampener working, Laurel's power was nullified, with Felicity taking advantage by giving her a knuckle sandwich. With Black Siren in custody, Ollie now takes on another mission: molding another Black Canary.

The viewers are then treated to some flashbacks in Russia, wherein Gregor gives the strongest line on the episode: "circumstances are what makes a thing poison or nectar."

Talia was also seen by the end of the flashback, hinting the first meeting of the soon to be mentor and trainee. The episode also hints another "canary", when two men in a bar were thrown off (literally) by a lady with her sonic cry.

Also, the episode saw John Diggle's (David Ramsey) transfer delayed, with the help of DA Adrian Chase (Josh Segarra).

"Arrow" is aired every Wednesday on the CW.