Team Arrow rallies at Palmer Tech to set up their plan of attack. Malcolm starts barking orders about containing the bio-attack and mobilizing a task force. Smoak and Laurel don't really like his tone, but Dig says they have to listen to him right now.
Ollie and Nyssa drop in (literally, they fall from the ceiling) and calm, level headed Dig reacts to that by clocking Ollie on the jaw. Everyone leaves during this moment of intense crisis so Ollie, Smoak and Dig can have a leisurely chat.
Ollie starts in with the explanations: He had to keep Malcolm close to learn about the League; he had to stay in Ra's' good graces to find out how he would attack Starling (which was definitely going to happen as part of Ollie's ascension). Oh, and also, he was definitely planning to die on that plane as a means of killing Ra's. Fully half of Ollie's plans this season have involved dying.
Dig can't believe Ollie would trust Malcolm before he trusted him. Smoak's more upset about Ollie's death wish. Ollie insists that it was "the only way," but it clearly wasn't because they're fighting Ra's now, and he's alive. Ollie says he's glad he lived so he could apologize to his friends. Dig won't accept it, but quickly pivots to "we've got bigger fish to fry."
The team launches into investigation mode. Nyssa and Dig discover that Ra's hasn't contacted any local League cells. Smoak has discovered several weird occurrences around the city — power spikes and the like — and one of those involves the top floor of a hotel being closed off for one Damien Darhk, Ra's' old nemesis.
Ollie figures that Ra's had an ulterior motive for wanting to wipe out Starling: Kill Darhk in the process. He decides to go grab Darhk and hand him over to Ra's. Malcolm calls the plan "incredibly cold-blooded," so he approves.
The team quickly secures the hotel and Ollie swings down to face down Darhk. What he gets instead is a low-rent Bill Nighy who quickly reveals he's not Darhk at all, just some lackey in a suit who is there merely to say Darhk skipped town when he found out Ra's was there. He's also there to die, which he does when an arrow comes flying in from behind him.
Ra's speaks to Ollie via the lackey's cell phone (I think, or maybe he's just got a direct line into Ollie's brain at this point), telling him that he set his bio-weapon plan in motion 10 minutes ago (like a less-punctual Ozymandias, which they already kind of pulled in season one's finale). Not only that, he's releasing it in four different places via four "instruments of death." Team Arrow can't get to them all in time!
Look, Ra's, babe. I'm not here to tell you how to unleash your supervillain plans. You're the expert. But maybe just let the hero believe you're only unleashing it in one place while you really release four, so that the plan definitely works? Just a thought.
After a brief scene where Laurel gets the cops on Team Arrow's side (more on that in a bit), everyone splits up and tries to find those "instruments of death." Apparently, the alpha/omega gives off a bit of a signature visible by satellite, like radiation, so Smoak and Palmer can see it. Palmer works on getting his ATOM suit outfitted with an "inoculant" to help contain the virus while the rest of the team sets out their assigned locations.
In his spot, Dig sees a guy carrying a briefcase and starts chasing him down. He catches up to him, but the guy pulls a sneak attack and bonks Dig on the head with the briefcase. It looks like he's got Dig dead to rights, but then, Thea, in Roy's Arsenal costume (but it's totally redesigned and fits her now) shoots the guy with some arrows.
Dig opens the briefcase and finds it empty. He quickly deduces that it's the guy himself that's carrying the bioweapon. The dude slits his own throat, which...releases the gas, I guess? Makes him more contagious? I don't know how this virus works.
Dig starts telling the good citizens of Starling to stay back, so, of course, they panic and run wildly in every direction. Some get infected. Starling crowds are the most consistent characters on the show. Too bad they didn't have homemade signs. That was a missed opportunity.
Elsewhere, Malcolm, Canary and Nyssa take down additional virus carriers. When Canary takes down hers, Nyssa observes that she trained Laurel well, which means maybe, finally, terrible fighter Laurel is a thing of the past.
They all say they're going to take the bodies of the infected dudes somewhere safe, but we don't see where that is.
During all this, Ollie just chills out on top of a building giving out orders. Ra's calls him up and invites him to fight him at Starling City Dam. Ollie asks why he should do that instead of saving the people of Starling, and Ra's says it's because Ollie definitely wants to know if he can beat him in a one-on-one fight. That's enough to get Ollie to abandon saving thousands of people to fight an end boss one more time.
When Ollie arrives, Ra's says he actually wins either way. If Ollie kills him, he takes the mantle of Ra's al Ghul. If he kills Ollie, the city dies. They start fighting. As they do, Ra's observes that Ollie has changed, in that he wants to live now (more on that later).
Just beyond the dam, a cop watches the fight and tells Captain Lance that he has orders to shoot both Ra's and Ollie when he can get a clear shot. Lance says, "Hey maybe don't?" but the cop says the orders override Lance's authority (who the hell are they from, then?).
Lance calls Smoak and warns her about this. Smoak turns to Palmer and says he has to take the ATOM suit to the dam to save Ollie. Palmer, quite rightly, says that he's preparing the suit to go save thousands of people from a bio-attack. Smoak goes, "But Ollie!"
Back on the dam, Ollie stabs the ever loving crap out of Ra's. As he's dying, Ra's says he chose his successor well. Ollie says the prayer Ra's said when he stabbed him on the mountain, and Ra's dies.
Just then, the cops shoot Ollie off the dam, and Atom flies in and grabs him before he can hit the water. They land elsewhere and — guess what — it's Smoak in the suit. Smoak says she'd kiss Ollie, but she can't get the helmet off.
Later, on Starling's One News Station, a report states that the virus was contained by an inoculant rumored to have been developed by Palmer Tech. So wait, how did Palmer get that out to everyone? Smoak took his ATOM suit. Are there two of them?
Also, did he synthesize a cure for the virus that Shrieve said last week there is definitely no cure for? Or did the people who got infected die? We'll never know.