What's arguably the A plot of this episode is Roy taking the fall for Ollie and going to prison for it.
And let's get this out of the way first: The Starling City legal system remains one of the most screwy legal systems around. Roy goes to full-on Iron Heights Prison seemingly without ever having his bail set, being arraigned, or having even an opportunity to talk to an attorney. Maybe he refused representation, since he's dead-set on being found guilty, or maybe he copped a plea and the episode just skipped over it? I'm probably the only person interested in the legal details, so let's just move on.
The highlight of the episode is the shot of Roy, in full Arrow costume, being led into the police station while Starling City residents crowd around carrying homemade signs(!). Starling citizens' love of homemade signs is the number-one reason I keep watching this show.
Inside the station, Ollie, who is handcuffed to a desk, attempts to tell Captain Lance that Roy's just trying to save him. Before he can, Laurel (in her only scene of the episode) swoops in and tells her dad that the DA isn't charging Ollie with anything while charges against Roy are pending. Maybe you should see to getting Roy his own attorney while you're at it, Laurel.
Also: Is Laurel the only person who works in the DA's office now? Is that how she can make these unilateral, unethical decisions? Did she just start squatting in now-dead DA Manhunter's office and nobody noticed?
Captain Lance is upset that he can't keep Ollie, but he can't, so he lets him go, with the promise of more scrutiny to come.
Ollie takes the opportunity to casually stroll into the interrogation room where Roy is, because anybody can just do that, and tell him he's making a mistake. Roy says this is his chance to pay Ollie back for saving his life back in season one. Hey, Roy, remember when Ollie shot you in the leg just for fun a while back? I think that evened it up.
Roy adds that he deserves to be punished for killing that cop while he was crazed on mirakuru, and that's pretty much that. Ollie leaves.
Lance keeps his promise about investigating Ollie by showing up at Verdant with a warrant to search the basement. The cops bust the door down and find the Arrowcave down there. Hey, at least all my complaints from two years ago about how easy that secret headquarters would be to find are being addressed.
The cops only find one set of fingerprints down there, though: Roy's. Team Arrow planned this all out, and used that stuff you can buy at the spy store that erases all fingerprints except one person's. You know the stuff I'm talking about. That stuff that exists.
Next we see Roy, he is fully and completely in prison at Iron Heights. It's been like a day! But he's got a uniform and everything. People are hooting at him. He goes to talk to Thea, who has come to visit him in a very yellow visitation room.
Roy tells Thea he didn't want her to come see him, because he promised he wouldn't lie to her ever again. He tells her he's going to be okay in there, hangs up the phone, and leaves. Eyes fill with tears, but they don't drop.
Later, some rando prisoners gang up on Roy and try to stab him, but he beats them all up while taking a slash to the back. It's a pretty cool fight scene.
Lance and the cops show up at Theapartment and search the place. Thea storms up to Lance and tells him he won't find anything there, but Lance doesn't listen. Instead, he says Thea must be "complacent or the most naive girl [he's] ever met," which is pretty true, but is also a case of a pot pointing out the color of a kettle. Then Lance tries to guilt Thea into giving up Ollie by saying Roy got attacked in prison, and that his death will be Ollie's fault.
Lance's lieutenant (who we haven't seen in a while) also comes waltzing in and tells him that he's risking his position of authority by continuing to investigate Ollie.
Thea goes to Palmer Tech to tell Ollie about Roy being attacked, and Ollie flips out, almost getting into a fight with Dig about how he's got to go break Roy out of prison right then and there. Dig and Smoak both talk some sense into Ollie about how he's just going to get himself killed or arrested. Finally, it takes Smoak saying that Ollie is the "man [she believes] in" to convince him. (She nearly says she loves him.)
Lance tries one last thing: He goes to Roy's cell and tells him that he doesn't deserve to be there, and that he's not doing the right thing protecting Ollie. Roy does something exceedingly stupid and confesses to a wholly unrelated crime — killing that cop. Lance just gets up and leaves on that one.
Later, Roy gets attacked in prison again, but this time it's a guard doing the attacking, and this time it seems to succeed. Roy takes a knife right in the gut, and lays on the floor bleeding.
Ollie goes to Theapartment to find Captain Lance visiting with Thea there. He told her that Roy has been killed in prison, and he does the same to Ollie. On his way out, he basically tells Ollie that Roy's death is his fault.
Ollie goes to the ruins of the Arrowcave to look at arrowheads and almost cry, but not quite. Dig and Smoak walk in and milk the moment like they're pulling some crazy, morbid April Fools' joke. It's downright mean-spirited, but you know what, maybe Ollie deserves it.
Just as Dig and Smoak get to the crescendo of their "You're sure gonna be mad at us" spiel, Roy comes walking in, looking just fine.
Turns out the guard that stabbed him was one of Harbinger's ARGUS friends, who knows how to stab someone just so in the gut with a beta-blocker-laced knife so that they look dead, but they're fine. We get a flashback of Team Arrow planning this all out, and then we see Roy getting zipped up in a body bag, and that's the end of the flashback.
What the hell happened after that? How did Roy get out of the body bag? How was he not incinerated or buried alive? How was there not an autopsy or an embalming? Wouldn't someone at the prison or the morgue care about a missing prisoner body, especially the body of the guy who was supposed to be Arrow and admitted to killing a cop? How did this all just work out? Did the prison staff just dump him on the side of the road? What is happening in this city?
However any of that happened, Roy rides off into the sunset in his fancy Dodge Charger after Team Arrow says their goodbyes. I suppose he's driving into a spinoff series?
Ollie says he learned to let people help him because of the hilarious prank his friends pulled on him, making him think his protege died taking the fall for vigilante murders on his behalf. It all worked out!