Ambiguous Situation: Sending her acolytes and the family away, Barriss tells them that the coordinates in her ship's computer will take them to "an old friend" and that "she" will help them; who this friend is and how she can help isn't spelled out, though it's implied that Barriss is sending them to meet Ahsoka Tano.
The Atoner: Since leaving the Inquisitorius, Barriss has set herself up as a healer to undo harm rather than inflict it as she once did.
Badass Pacifist: Barriss completely undoes the Fourth Sister without ever laying a hand on her or drawing a weapon, simply dodging her attacks, then using words and the Fourth Sister's own vulnerabilities to drive her into breaking down and forsaking the Inquisitorius.
Break Them by Talking: With the Fourth Sister lost in the cave and losing her mind in frustration and fear of failure, Barriss verbally breaks her down, insisting on using the Inquisitor's birth name and deconstructing her boast that "fear is [her] ally", trying to compel her to abandon the dark side. Barriss is ultimately successful, though Lyn stabs her in a blind rage before coming to her senses.
Continuity Nod: The mother of the family informs Barriss that Imperials have been taking blood samples from their planet's children, no doubt to see if they have a high enough M-count to be useful to Palpatine's ProjectNecromancer.
Easily Forgiven: Barriss immediately forgives the Fourth Sister after she stabs her by accident.
Eldritch Location: Like the caves on Dagobah and Ahch-To, the cave Lyn chases the family through is just as unnatural as Barriss warned it would be. While the family safely navigates through it to reach their ship, an increasingly frustrated Lyn finds herself repeatedly going in circles well after her quarry makes the jump to hyperspace.
Expository Hairstyle Change: Barriss sports a much shorter hairstyle than in any of her previous appearances, giving her a noticeably gentle appearance befitting her new lease on life as a sagely healer.
Impaled with Extreme Prejudice: The Fourth Sister accidentally impales Barriss with her lightsaber while recklessly swinging it around trying to escape the caves. The episode ends before we find out if Barriss died from it or not.
Irony: An in-universe case. The Inquisitors had long given up looking for Barriss, when the Fourth Sister finds her entirely by chance.
Maybe Magic, Maybe Mundane: It's unclear if the cavern system is normal and Lyn's clouded judgement causes her to get lost, or if it's deeply connected to the Force (just like the caves on Dagobah, Ahch-To, and Illum) and deliberately traps Lyn in response to her fears.
Motivated by Fear: Although the Fourth Sister boasts that "fear is [her] ally", her response to Barriss' offers of redemption makes it clear that she's very much afraid of incurring the wrath of her superiors; as Barriss notes, rather than her ally, fear is Lyn's master.
My God, What Have I Done?: The Fourth Sister is horrified when she accidentally stabs Barriss with her lightsaber.
Nonchalant Dodge: In another demonstration of just how weak the Fourth Sister is compared to Barriss, Barriss effortlessly avoids all of her swings and lunges with her lightsaber and uses the Force to casually block a swing and push her away.
The Soul Saver: Having achieved redemption for herself, Barriss takes the opportunity to push Lyn onto the same path when her former friend comes to call. After some effort and a potentially fatal stab wound, Barriss manages to get through to Lyn, who's last seen doing all that she can to save Barriss' life.
Tempting Fate: When Barriss warns her of how easy it is to get lost in the cave, the Fourth Sister arrogantly replies that fear is her ally, not Barriss'. She ends up getting hopelessly lost, and her fear of her masters' wrath is used against her by Barriss.
Time Skip: Barriss' visible aging makes it clear that it's been many years since she left the Inquisitors, and the Fourth Sister admits that the Inquisitorius almost gave her up for dead after a long period with no sign of her.
Uncertain Doom: Barriss accidentally gets skewered by the Fourth Sister near the end and the episode ends without revealing whether or not Barriss managed to survive.
Villainous Breakdown: Trapped in the cave and driven over the edge by frustration and fear of her masters' punishment, the Fourth Sister starts angrily slashing at the walls around her in a blind fury, only coming to her senses when she accidentally stabs Barriss.
What You Are in the Dark: Interesting example with the Fourth Sister. When she's trapped in the cave with no way out, she slashes at the walls. Specifically, she's slashing at the reflections of herself. Is this a sign that she hates what she did for the Empire? Is she frustrated with her failure to do the Empire's bidding? Is she just afraid of this person she has become? Whatever the case, when she has stabbed Bariss and has no one to call for help, Lyn decides she's going to help Bariss and carries her out of the cave.
Would Hurt a Child: The episode opens with a family seeking Barriss out for help after the Empire identified their baby as Force-sensitive. Sure enough, they're being pursued by the Fourth Sister, whose intentions for the child are clearly not good.
You Have Failed Me: Alluded to; lost in the cave and offered a chance at redemption by Barriss, the Fourth Sister initially refuses, asking if Barriss knows what "they" (presumably Vader and the Grand Inquisitor) will do to her for failing her mission.
