Arrow 5.10, "Who Are You"

There is no way to discuss this without les spoilers.

The episode opens exactly where the previous one left off, with Ollie in the Arrowcave, surprised that Laurel is back. According to Laurel, she was saved by Sara and the Waverider, doing something with time. Of course, anybody who's watched Legends knows that not only has Sara not attempted to save Laurel during the events of Arrow 4.18 (because "time punches back" or some such - look, the rules of time-travel on that show are whatever they need to be to satisfy that episode's plot, just roll with it) but has rather spent the year trying to save Laurel by murdering Damien Darhk prior to 2016. So that's Big Honkin' Red Flag Number One.

Felicity is suspicious and probably jealous. I mean after all, she still wants Oliver, and Laurel is pretty much the only other woman in his life. So with Laurel back from the dead, and Felicity's love life screwed up by the whole "Oliver killed Billy by accident" thing... I do see some green eyes there, Felicity, I see 'em.

Well at any rate, one of the other characters points out that, hey, it's not like Laurel has an evil twin or anything... and Felicity's all oh wait yes she does and then everything goes to hell.

Okay, so Barry told them off-screen. Fine, whatever.

The team captures Black Siren, who says that she's being coerced into working with Prometheus (now why would Prometheus go out of his way to spring her from the Pipeline? Hmm.) She's all bad because on Earth-2, Oliver (and presumably Sara) died when the Queen's Gambit went down, and unlike their Earth-1 counterparts, they actually did die, and stayed dead. She drifted to Central City (whereas her Earth-1 counterpart coped via a fling with, um, Tommy Merlyn) and was there when the particle accelerator did its thing.

Felicity rigs Siren's power-damping cage to malfunction, so Siren "escapes" and leads them to Prometheus, but they wind up fighting Siren again. I'm not going into how exactly they beat her (it's mind-bogglingly stupid) but they do.

Adrian Chase is tasked with preventing Diggle's extradition. He accomplishes this by getting Diggle to punch him and then charging him with assault. That's... novel.

Meanwhile in the flashbacks, Oliver is being held captive by some-Bratva-guy-whose-name-I-don't-remember, until Talia shows up and murders everyone.

There's a lot going on here with Oliver's guilt complex, Felicity getting increasingly unstable (ordering the team to kill Laurel during the capture mission, rigging the cage on her own initiative), and the revelation that Prometheus knows enough about the Legends to feed Siren that cockamamie story about being resurrected by the Waverider. This dude did definitely not learn that Oliver was Green Arrow from Church.

Look, Katie Cassidy owns this episode, although the nose-ring is really, really distracting. And thanks to behind-the-scenes shenanigans we know about, we know this isn't the last we'll see of her this year (she's slated to appear on all three shows; I'm really looking forward to the Siren/Canary showdown on Legends).