The season finale of The Acolyte begins where episode 6 ended; Osha is wearing The Stranger's helmet, but appears to be losing control, forcing the mysterious Sith villain to help her remove it.
She had a vision of Mae killing Sol with one hand outstretched and a lightsaber in the other. This means her twin makes good on her promise to kill a Jedi without a weapon, prompting The Stranger and Osha to head to Brendok together.
On Sol's ship, he argues with Mae about who should be blamed for what happened on the planet sixteen years ago. She breaks free and flees in an escape ship, prompting the Jedi to chase her down. However, as he readies himself to shoot her out of the sky, Bazil intervenes and they both crash on the planet below.
Supergirl star David Harewood shows up as Senator Rayencourt, a Jedi-hating politician who wishes to hold the Order accountable. He threatens Vernestra Rwoh with an external enquiry, putting further pressure on her to keep the recent murders under wraps.
The Stranger offers Osha her last chance to join him as they leave his home and it's then we see a shadowy figure in the cave they were in watching on: yes, it's Darth Plageuis! We don't know whether he's Qimir's secret Master, a rival Sith looking to eliminate a rival, or simply hiding out on a planet which we can now say is almost certainly meant to be Bal'demnic.
What we do know, of course, is that he'll one day become Emperor Palpatine's Master, figuring out how to create life through the Force and to escape death. Something tells us a being like Osha will be key to that.
Sol and The Master clash on Brendok in an epic lightsaber duel, while Mae and Osha also come to blows. The latter reveals that her hatred for her twin and her grief is what stopped her from becoming a Jedi. She doesn't believe that Sol killed their mother but a little later on, he confesses to Mae (who refuses to kill him at The Stranger's request and instead argues the Jedi should pay for his crimes in front of the Senate).
Sol confirms their mother used the Force and a vergence on Brendok to create Mae and Osha as his former Padawan watches on. Picking up her old Master's lightsaber, she refuses to listen to his pleas and, as he goes to tell her that he loves her, she uses the Force to choke him to death. As she does so, the blue Kyber crystal in Sol's blade turns red.
Vernestra senses Qimir and it's essentially confirmed that he was once one of the Jedi's pupils before whatever happened that left him with that lightsaber scar on his back.
Mae and Osha finally move on from the past but there's no happy ending for them, unfortunately. The Stranger says he will teach Osha, but if the Jedi apprehend Mae, she'll have no choice but to reveal where they are. With their permission, he wipes Mae's mind to make it so that she forgets her sister, though Osha does vow to one day find her.
Mae is arrested by the Jedi and remembers nothing of what happened to her after that fateful night on Brendok. Vernestra tells the Chancellor and his Senators that Sol murdered his fellow Jedi to cover up his past actions, explaining why no one knows about the Sith's return. Now, she needs Mae's help finding a pupil of hers before he turned to evil...so yes, The Stranger was once a Jedi and the cover-up will likely continue.
The episode ends with Qimir holding Osha's hand as she becomes his Acolyte and, back on Coruscant, we catch a glimpse of Yoda as Vernestra tells him they need to talk...