In “Lethe,” the sixth episode of Star Trek: Discovery, everyone has something to hide. But the character with the biggest secret is easily Spock and Burnham’s dad, the famous Vulcan ambassador, Sarek. The latest Discovery twist redefines a pivotal moment in Star Trek’s past, making Sarek way more sympathetic than he ever was in the original series.

Spoilers ahead for episode 6 of Star Trek: Discovery, “Lethe.”

“He’s made some decisions that are extremely bold,” James Frain tells Inverse. After Mark Lenard and Ben Cross, Frain is the third actor to play Sarek, and he doesn’t take the responsibility lightly. Frain is also in the position to explore the character more realistically and complexly than his predecessors. “In the original series, we’re looking at Spock, and Sarek is part of Spock’s backstory. But, he’s now becoming his own character. Who is this guy who married a human? Let’s track back on that”

While Sarek is enroute to a secret peace conference with the Klingons, a xenophobic Vulcan extremist group sabotages his ship with a suicide bombing, leaving him adrift in space and dying. Through her unique quasi-telepathic connection with Sarek’s katra, Burnham senses her foster father is in peril, and so, the USS Discovery mounts an impromptu rescue mission to find Sarek’s damaged ship somewhere in a nebula. In order to find out exactly where Sarek is, Burnham has to attempt another long-distance mind-meld, augmented by some tech from Stamets. Entering Sarek’s mind, Burnham discovers her Vulcan foster-father’s dying thoughts are dwelling on the day of her graduation from the Vulcan Science Academy. But why?

Sarek reaches across space with his mind to give Burnham a pep talk in "Battle at the Binary Stars" CBS

“One of the interesting things about this flashback scene in this episode is we see Sarek in an almost a childlike position, with a senior Vulcan who is presenting him with this impossible choice, punishing him, essentially,” Frain says. After literally fighting with Sarek’s subconscious, Burnham convinces him to reveal his most shameful secret. Up until this point, Burnham had believed that a nifty space program called the Vulcan Expeditionary Group had rejected her application, but now it turns out she was accepted and Sarek lied to her about it. Instead, Sarek choose to deny Burnham entrance into the Vulcan Expeditionary Group for one simple reason. The elder Vulcans in charge forced him to choose between Spock and Burnham saying “we’ll accept one of your not quite-Vulcans”; referencing the fact that Spock is half-human by his biological mother, Amanda. If Sarek had picked Burnham, the elders would have denied Spock’s entrance into the group, and probably the science academy. And so, Sarek told Burnham she wasn’t accepted and took her to live with the Starfleet crew of the USS Shenzhou instead.

“That was very interesting,” Frains says. “Sarke’s kind of like the child in this scene. He’s vulnerable. He has the power taken away from him. And has to make a choice where there’s no winning.”

Spock and Sarek in 'Star Trek VI'

For those familiar with Spock and Sarek’s estrangement in the original episode “Journey to Babel,” this adds a layer of cruel irony. Because Spock decided not to attend the Vulcan Science Academy on his own, we now know Sarek’s choice of giving him the opportunity was totally moot. In Sarek’s mind, he hurt and betrayed Burnham for no reason, and retroactively, views it as partially Spock’s fault. And if you add in the fact that Sarek’s full-blooded Vulcan son, Sybok, also ran away from home, Sarek’s inferiority complex as a father is getting pretty serious. But, because Sarek lied about the Burnham thing, he hasn’t really told anyone about the entire situation.

After saving Sarek’s life, Burnham visits him as he convalesces in the sickbay of the Discovery. Similar to another sickbay scene, the ending of “Journey to Babel,” Sarek acts as though nothing has happened, pretending as though Burnham’s entrance into his mind is something he never really experienced, due to his near-death condition. In essence, his cold, logical exterior has returned, preventing him from having a healthy relationship with his daughter. But, the difference this time, is the audience actually feels sorry for Sarek now. Before, he was just kind of cold-blooded asshole who disapproved of his son hanging out with humans.

Now, we see him as a guy who really loves humans, but that love has made his life more difficult than it would have been had he followed a more traditional path. This episode also added another interesting wrinkle because we learned that the bombing at the Vulcan Learning Center when Burnham was just a little girl wasn’t perpetrated by Klingons, but instead, by the same terrorist Vulcans who tried to kill Sarek.

Sarek rescues a young Michael Burnham from a terrorist bombing perpetrated by extremist Vulcans.

“Sareks’ decisions have put him in a position where there are Vulcans that are trying to kill him.” Frain explains. “We’re not trying to skate over that. He adopted Michael and they tried to kill her and then he gave her a piece of his soul. You get a lot of who he is by those actions. But it’s still fascinating that he’s the first ever Vulcan to do this. And he believes in it enough that he’s putting his life on the line and the life of his family.”

Star Trek: Discovery airs on Sunday nights at 8:30 pm eastern time on CBS All-Access.