All of Harvey's efforts to negotiate and maneuver a way out of Ava Hessington's murder trial come to naught, because the thing is actually happening. Even though our team knows that Stephen Huntley was the one who gave the order for Colonel Mariga to kill the pipeline protestors, they have no way to prove it. And even though Darby has known it for a while, he has avoided discussing it with Stephen to provide himself deniability, so there's no help coming from that weasel. Mike tries to convince Mariga to tell the truth rather than the story that's part of the deal he cut with Cameron, but Mariga is sticking to the original narrative because he figures it's the best way to avoid being sent back to his homeland and certain death. And Harvey doesn't get much further when he tries to convince Cameron that he knows who the real culprit is.
So during the trial, Harvey throws a Hail Mary and puts Stephen on the stand. He knows Stephen won't cooperate, but he's trying to communicate his guilt to Cameron Dennis. Unfortunately, Cameron treats this move as a desperate stunt to divert suspicion from Ava, and Stephen uses his time on the stand to mention Ava's previous attempts to bribe witnesses. Which makes her look pretty guilty in front of the jury.
Ava's pretty mad when she finds out that Darby was aware of Stephen's part in all this and kept her in the dark. Darby explains to Jessica exactly how Ava is like family to him, which gives Jessica an idea. After Mike's attempt to talk Cameron out of prosecuting the wrong person by reintroducing him to his wrongly convicted defendant from season one fails, Cameron offers Ava a deal: eight years in prison. Finally Darby steps up. He tells Cameron that he set Stephen loose and offers to testify at Stephen's murder trial, in exchange for five years of probation for obstruction of justice. So the murder case is over.
Meanwhile, in their increasingly permanent B-plot ghetto, Louis is rekindling his feud with Harold after last week's cat trial while Rachel provides paralegal and expositional support. Harold retaliates against Louis by suing one of Louis's clients, and soon finds himself outmatched. But then, when Rachel gets Louis to admit his reasons for hating Harold, Louis relents. It's better than the cat trial, but not by much.
Finally, when Darby sits down to sign his deal with Cameron (with Jessica, Harvey, and Mike also in attendance), he discovers a new provision wherein he also loses his license to practice law in the U.S. Jessica set that up as part of the deal, so now the merger is effectively over. I'm just not sure why the season isn't.
Harvey's back in his office, getting patched up by Donna after beating up Stephen Huntley in the men's room. Mike and Jessica must have wandered off during the interim. Donna's feeling awful about not having realized that her now-ex-boyfriend was a lying sneak who ordered the killings for which Harvey's client Ava Hessington is about to go on trial, so Harvey tells her that Stephen betrayed all of them. "Just tell me you're gonna make him pay," Donna asks. Harvey is glad to oblige. What's he going to do, beat him up again?
Harvey then goes down to see Mike, who's at his desk in the otherwise empty bullpen. He tells Mike to keep working on impeaching the testimony of Colonel Mariga, the man whose troops did the actual killing and who is now the prosecution's star witness. As for Stephen, Harvey says they don't have enough proof of his involvement to use in Ava's defense, or even alert her yet. So for now, Harvey's going to go home, sleep, and find out what the whole story is. Mike warns that Stephen won't tell him that, but Harvey says someone else can.
The next morning, Harvey and Jessica are grilling Edward Darby in her office. Turns out this case was his reason for wanting to merge in the first place, and though he admits he knew about Stephen's involvement after the fact, he denies having given Stephen the order regarding the killings. Darby claims that he sent Stephen over because of how much he cares about Ava, but when Jessica invites him to say in court that Stephen acted on his own without Ava's knowledge, he begs off, saying Stephen never told him and he never asked, so he doesn't legally know. Harvey calls Darby a piece of shit for leaving Ava twisting in the wind like this, and Jessica informs Darby that he's going to do something for her right now.
And…cut to Stephen in his office, locked out of his computer and unable to get his desk phone to work. Donna's there, saying this all is her doing, to get his attention. She has some calm yet harsh words for Stephen, calling him a murderer. Stephen starts mansplaining to her about the moral complicity of the designers who make her clothes, not to mention that of any number of Harvey's corporate clients. Donna gets bored and says the real reason he's cut off is because he's fired. Stephen doesn't believe Darby would allow that, so Donna informs him that Darby signed his pink slip an hour ago. So chew on that, Stephen.
Louis has just finished chewing out the associates in the bullpen for their shoddy work in his absence when Rachel intercepts him on his way out of the bullpen, wondering why he just shit on the people who put him back in charge. Louis doesn't see it that way, saying, "They made me give up Mikado for them." Rachel says they didn't put Louis in this position. "But I know who did," Louis says. Uh, the idiot who sued for someone else's cat in the first place?