SPOILERS for Star Trek: Discovery!
As Star Trek: Discovery plots its course towards the endgame of season 1, mysteries that have been simmering all season long - some of which are not surprises to many fans - are being solved at warp speed. At the top of that list is the truth about Lieutenant Ash Tyler.
Last week's episode 'The Wolf Inside' saw Tyler come face to face with the Voq of the Mirror Universe, also known as the Fire Wolf, who was the leader of the Klingon/Vulcan/Andorian/Tellarite coalition opposing the evil Terran Empire. Fans had long held the theory that Ash Tyler was actually Voq, surgically altered to appear human. Since the Discovery was stranded in the Mirror Universe, that theory has been confirmed. Ash Tyler is really Voq, and Ash/Voq made that clear to Michael Burnham before she had him seemingly executed on board the I.S.S. Shenzhou. In reality, Burnham had Ash/Voq beamed onto the Discovery, where the ship's surgeons have been unable to help him.
In this week's episode 'Vaulting Ambition', we learned the answer to another question surrounding Ash/Voq: Was there really a Lieutenant Ash Tyler before Voq was surgically altered to appear human? Did a human Starfleet Officer with that identity actually exist? After all, when Ash/Voq became the security chief of the Discovery, he passed Starfleet medical exams and background checks. That and the many stories of his past he told Burnham and Captain Lorca indicated that there really was an Ash Tyler, but it wasn't confirmed.
None other than First Officer Saru received the confirmation from L'Rell. With Ash/Voq resisting Starfleet's medical aid, Saru visited L'Rell in Discovery's brig to ask her help to ease Ash/Voq's suffering. The Klingon/human hybrid has been experiencing bouts of mania and shifting between his Klingon and human personae. As Saru deftly summarized it, the war between humans and Klingons the Federation and the Empire had been fighting was taking place within the body of the man Saru knows as Ash Tyler.
At first refusing to help Ash/Voq, L'Rell revealed more about how the Klingons turned Voq into Ash Tyler: There really was a Starfleet Lieutenant Ash Tyler who was captured at the Battle at the Binary Stars. To turn Voq into Ash Tyler and fool the humans into accepting him as one of their own, the real Ash Tyler's DNA was harvested and his consciousness was reconstructed in Voq's mind, laid over Voq's personality. (The Klingons of Star Trek canon have mind control technology, like the mind scanner they boast of in The Original Series episode 'Errand of Mercy'.)
L'Rell made it very clear (supported by Tyler's gory flashbacks of his surgery) that Voq is living in Ash Tyler's shell. She did not, however, confirm whether the original Ash Tyler is dead or not. It's possible the human captured at the Binary Stars is still a prisoner of the Klingons after his DNA and memories were stolen for Voq.
After telling Saru that what the Klingons did to Ash/Voq can be undone, Saru allowed L'Rell to perform a procedure where she wiped Voq's personality from Ash Tyler, seemingly killing the Voq part of him. When it was over, L'Rell roared the way Klingons roar when a Klingon dies, indicating the former Torchbearer of T'Kuvma has indeed gone to Sto-vo-kor. Though he remains a hybrid of a Klingon surgically altered into a human but with his Klingon persona wiped clean, only the human personality of Ash Tyler now exists.
Considering how commonplace a Klingon being surgically altered to appear human will become, such as Arne Darvin in 'The Trouble With Tribbles', and later humans vice versa being turned into Klingons, like several members of Star Trek: Deep Space Nine were in 'Apocalypse Rising', Ash Tyler is the first of his kind and suffered the most from the procedure. Within a decade, it seems the kinks will be worked out without all of the trauma.
Star Trek: Discovery streams Sundays @ 8:30pm ET on CBS All-Access, in Canada on Space Channel, and worldwide on Netflix.