At the end of the last episode, Malcolm Merlyn discovered that the hooded vigilante he'd just beaten into unconsciousness was, in fact, Oliver Queen. So this episode begins with Oliver dangling from some chains while Malcolm monologues at him about how he's doing the city a favor by destroying the Glades. Then Malcolm leaves him alone so he can escape, because there are rules to this sort of thing. Oliver goes straight to his mother and demands that she stop the Undertaking, but she says she can't. Oliver tries calling Quentin Lance to warn him, but that just results in Quentin being suspended from the force for talking to the vigilante. And then Moira goes to the press to confess everything.
Moira's decision to go public is great in principle, but it doesn't really accomplish anything aside from getting everyone in the Glades to start panicking and looting. Thea finds Roy, but he won't get to safety because he'd rather help people. And Oliver has to get his team on the case. After some negotiations, they decide that Oliver and Diggle will go after Malcolm, and Felicity will talk Quentin through the process of disarming the earthquake device. By the time Oliver and Diggle reach Malcolm's office, he's already killed three policemen and knocked out Tommy. Tommy is now sorry he doubted Oliver. But that doesn't matter, because Malcolm is hiding in his own Arrowlair, and it's time for the big season-ending fight.
Back on Flashback Island, Fyers launches a missile at that plane. Then Oliver, Shado and Slade get loose and start laying waste to everybody. Shado manages to reprogram the missile to turn around and hit Fyers' camp, which kills everybody except the named characters. After the flames die down, Fyers takes Shado as a hostage and tells Oliver he could get a boat off the island. Instead, Oliver shoots an arrow through Fyers' neck. So there!
Oliver manages to kill Malcolm, and Quentin manages to disarm the earthquake device. But just as everyone is breathing a sigh of relief and deciding where to get some drinks, they discover there was a second device. And the earthquake it creates is localized to pretty much just the couple blocks around CNRI. So of course Laurel gets stuck under some concrete. And Tommy races in to save her! But as she gets out (and into her father's arms), the building collapses, and now Tommy's trapped. So Oliver rushes in to save him. But it's no use, and Tommy dies. Like I said he would. Rough episode for the Merlyns, huh?
Season finale! Let's go! Are you pumped? Get pumped! Maybe not as pumped as Stephen Amell, but still.
After the previouslies, we open in the lifeboat from the Queen's Gambit. Robert Queen tells Oliver to right his wrongs. Then he shoots that other guy (whose presence has never been explained) and himself. This scene already happened on the show, so maybe it was part of the previouslies. I don't know, man.
In new business, Oliver is shirtless and dangling by his wrists from some chains. A little something for the ladies! And also a lot of men! He is awoken by a bucket of water being thrown at him. Malcolm says he hopes he didn't hurt him. Somewhere around now, it dawns on Oliver that Malcolm now knows he's the vigilante. Malcolm thanks Oliver for saving his life that time, and now he's going to explain everything, which he believes will get Oliver on his side. Oliver complains about Malcolm murdering his father, being murdered and stranding him on the island. Malcolm apologizes. See, he's a nice guy! Malcolm believes he's honoring Tommy's mother by destroying the Glades, just as Oliver is honoring Robert with his hood-related vigilante activities. Malcolm has a theory on why Oliver has been defeated by him twice, even though he's younger and fitter. I don't think Oliver knows that he's fought Malcolm more than once, since Black Arrow is still a mysterious figure. But there's no time to worry about that sort of thing, since Malcolm is building a case. It's because Oliver doesn't know what he's fighting for, and Malcolm does. And he says no one can stop what's coming, adding, "Not even the vigilante." He tosses the hood on the floor and leaves.
Flashback Island. Oliver, Slade and Shado are tied up in the command tent. A plane flies overhead. The radio guy announces that Missile One is locked on target. Oliver saws at his bonds and attacks! Shado also attacks, although she needs Oliver to cut her bonds. He does and it is on. Slade also does some fighting, and it's mayhem. The tent gets cleared out, but the missile launches from the tank anyway.
Modern day. Oliver has been left alone to dangle from chains. Oliver pulls himself up so he's upside down. It's very impressive. Then he climbs the chain upside down, which is just showing off, in my opinion. After he gets pretty high, he lets himself drop, so when he hits the bottom, the chain breaks the pipe that the chain was looped around. I would have thought Oliver's wrists would also snap off, but I guess not.