Jennifer, now living under a new identity in Beacon County, becomes aware of the presence of the Alpha Pack in Beacon Hills. She moves up her plans to perform a full five-fold knot of human sacrifices in order to bestowe supreme power upon herself. With her decision put into action, animals start to react alarmingly to her action; pets start behaving aggressively, cats commit suicide by self-mutilation and a deer charges down the middle of the road and commits suicide by crashing head first into Lydia Martin's car.
"This is the last line to the first book we're going to read. It is also ... " (holds up her phone) " ... the last text you will receive in this class." - Jennifer to her class
She instructs all the bemused students to turn their phones off and put them away. Later during class, the principal comes in and talks to Jennifer. She tells Scott that his mother called for him. Jennifer reminds Scott of his attendance record from last semester, but is assured that it's an emergency. Scott apologizes to Jennifer for having to leave, and she admonishes him to not make a habit and that resolutions only succeed when one sticks with them. Scott reassures her he won't be "ephemeral" to her amusement.
She orchestrates another animal sacrifice to take place by summoning a flock of ravens. Suddenly, a raven slams into the window, killing itself. Jennifer walks away from the board to investigate. The entire flock of ravens are flying towards the classroom.
The birds fly straight into the window, eventually breaking through the glass and flap around the classroom, pecking students and crashing into walls, desks and everything in the classroom. Jennifer springs into action at once and screams at everyone to stay down, shielding a boy's face as the sacrifice takes place, fuelling her abilities.
After the animal sacrifice ends with the birds having died upon impact, everything calms down. Paramedics are present though nobody is seriously hurt. Jennifer appears stressed. Stiles tries to comfort Jennifer then awkwardly tries to pluck a feather out of her hair to her distress.
The following night, Jennifer goes out as the darach, preparing to start the Virgin sacrifices. She heads to a birthday party held by Heather who is a virgin selecting the teenager as her first target. Stalking the girl in her house's wine cellar, Jennifer casts illusions upon Heather, displaying an earthquake then the wine bottles sliding off the racks, then exploding and glass raining down on the girl. Once Heather is cornered at the window, Jennifer snatches the girl.
Jennifer then kills Heather, using the threefold death, performing a druidic chanting while abducting and killing her, executing her first Virgin.
The following night, the Darach is out to take two more virgins. She again performs the threefold death on a young man named Noah, a lifeguard at Beacon Hills' public pool. Afterwards, she then stalks a lesbian couple Emily and Caitlin. Casting an illusion depicting a swarm of bugs to frighten Emily, Jennifer uses her magic to teleport Emily to her. She kills Emily, again using the three fold death, binding her corpse to a tree. Jennifer has now completed the virgin sacrifices.
At the high school, Jennifer is working late at night. The werewolves Boyd and Cora Hale are on a full moon induced rampage. She goes down to the supply closet in the basement conncted to the boiler room. Jennifer gets locked in when Scott and Derek close Boyd and Cora up in an attempt to keep the savage werewolves contained.
Jennifer then cowers and slams the door to the closet shut. Jennifer recoils in terror, petrified and listens as Derek allows himself to be shredded himself to be shredded by the two betas. After the sun comes up, Boyd and Cora pass out and he goes to Jennifer, mistified. She still appears fragile, but he offers her his hand to help her to her feet.
Jennifer uses the power she gained from the virgin sacrifices on Derek, mystically roofying him, leaving the alpha drawn to her.
Several days later, Jennifer turns her attention to Warrior sacrifices. She tracks down a senior Kyle with a military background and his dog Bullet drugging them both with mistletoe. She lures the dog towards her after they leave the animal clinic and manifests an illusion drawing Kyle to her. The young man sees himself being bitten by the dog, when in reality the dog is sitting behind him. Jennifer then psychically changes her voice telling Kyle to "come closer." She snatches the confused young man teleporting him to her, and kills him, sacrificing her first warrior.
Jennifer is at the school before classes start. She appears nervous and constantly looks over her shoulder after she hears a noise. She runs into her classroom, then sees that Derek is there letting out a yelp.
Jennifer: "Physically or emotionally? Though, I guess that pretty supposed I was emotionally okay before any of this and according to my therapist" (laughs shakily) ... it's been debatable for a long time."
Derek smiles amused and says she's going to be okay and gently takes the stick from her hands. her They flirt a little, and she promises not to tell anyone about what she saw. Derek, clearly attracted to her from the virgin sacrifices, gently hands her back the pointer and turns to leave. Jennifer calls and asks for his name, the alpha responds. Afterwards, she introduces herself.
Derek, badly injured, finds his way through town to the high school, where Jennifer is just getting into her car. He puts a bloody hand to her window and then collapses.
Jennifer brings Derek back to his loft because he refuses to go to the hospital. He's too heavy for her to carry his weight, and she drops him just inside the door. Eventually, she gets him onto the bed and starts checking his wounds. They're bad and bleeding black blood. She's somewhat flirtatious, but Derek doesn't respond one way or the other. He passes out, and when he wakes up, Jennifer is there waiting for him. He wants to call everyone and tell them he's alive, but she uses her power over him to convince him not to. She says that it could be to his advantage if everyone thinks he's dead. He tries to get her to leave so that she doesn't get hurt by being around him, but she refuses to go. Her magical influence over him wins out, they kiss and then have sex, Although it does not look forced due to the nature of her powers of influence from the virgin sacrifices, the tone of the scene makes it clear that there is nothing good about this and that she is, in fact, raping him. Derek's wounds healing as they get into it, potentially also due to her magic.
When Kali and the twins go to Derek's loft to fight, they bring Jennifer along as leverage. Kali wants Derek to fight her by himself, and the threat against Jennifer will ensure that. She watches as Kali and the twins use Derek's body to kill Boyd.
In class, Jennifer teaches the students about metaphors and idioms. She brings up "seeing the whole board" which Stiles recognizes as being a reference to chess. In between classes, she rushes outside to meet Derek, who has been gone for a few days dealing with Boyd's death. The overly romantic tone of the scene shows that he's still under her influence as they kiss, and Derek assures her that he'll keep her safe from the twins walking around the school. She tells him about the recital she's having at the school for all the people who have died recently. They kiss again, and then she heads back to class. Lydia finds a five-fold knot on the board in Mr. Westover's room and knows that he's been taken as a sacrifice. She told Jennifer, but Jennifer isn't convinced that there's any reason to raise an alarm. After school, she waits outside for everyone to come into the auditorium for the recital. When the music starts to play, Jennifer disappears into the school and fakes a text message to Lydia to lure her away. She had previous seen Lydia drawing images of the nemeton and needed to get rid of her. She knocks Lydia out and ties her up, taking the time to explain that the sacrifices she's been performing around town are necessary. Lydia isn't a sacrifice, though. Jennifer tries to strangle her, but Lydia gets her hand in front of the garrote and screams. It's Jennifer who reveals that Lydia is a banshee. The scream calls Scott and the Sheriff. Jennifer is about to cut Lydia's throat when the Sheriff bursts in. Jennnifer throws her knife into the Sheriff's chest and then attacks. Scott comes in but is quickly tossed aside. Jennifer then approaches the Sheriff revealing how each sacrifice gave her a different power. She ends by revealing her true face and kissing him. They vanish via magic.
After putting the Sheriff in the nemeton off-screen, Jennifer rushes to Derek's apartment to try to get to him before Stiles and Scott do. She tells him that he has to listen to her, and he promises to hear her out. When she kisses him, though, she can tell something is wrong. Scott and Stiles reveal themselves and make their accusation, which she tries to play off as foolish. Derek looks torn but seeing Stiles' distress over his missing father is enough to keep her influence over him at bay as he demands answers to their questions. Scott then uses mistletoe to reveal Jennifer's true form, and Derek grabs her by the throat. He wants to kill her, but she saves herself by pointing out that only she can cure what's wrong with Cora. Stiles further asks that Derek not kill her because she's the only one that knows where his father is. Derek lets her live, and the four of them head to the hospital to help Cora. Derek holds Jennifer by the arm as they walk to the elevator. She claims she isn't going to run but clearly none of them believe her. When they encounter the twins, Jennifer takes the first opportunity to run. She ends up in the same hallway as Duke and Kali and has to go back into the elevator to hide. She escapes back into the hospital and eventually finds Stiles, Scott, Derek, Peter, and Cora. She again says that she can save Cora but will only do so if they save her from the Alpha Pack. Angry, Derek launches himself at her but Scott stops him from attacking. Stiles asks her to heal Cora as a show of good faith, but she refuses. Melissa's voice comes over the PA asking for Jennifer to be turned over to Duke, but Jennifer is sure that Duke won't hurt Melissa because he wants Scott in his pack. She reveals that Scott is going to be a True Alpha.
They decide to try to run. Derek, Jennifer, Stiles, and Cora head for the ambulance. Jennifer finds the ambulance driver dead, and then Kali steps into view with the keys. Derek and Jennifer run and end up stuck in an elevator. While the others form a plan to get them out, Jennifer tells Derek about what happened to her. She reveals that her biggest fear is that he'll judge her for her ugly face. She also tells him the story of mistletoe as being the plant that was overlooked. The emissaries are overlooked as well, and she wants to be sure no one overlooks what the alpha pack did. Her plan is to attack Deucalion during the lunar eclipse, when he will lose all his power. When the power comes back on in the hospital, Jennifer knocks Derek out and then takes Melissa McCall as the next sacrifice.
Chris Argent gives himself over to Jennifer at Beacon Hills First National. While he's unconscious, she takes all his hidden weapons from him and ties him to a post in the nemeton. After he wakes up, she comes down at dabs at the blood on his face. She notes that it's interesting that the legend became that silver kills werewolves when really it was the Argent family. She explains that he should be proud of the sacrifice he's making because he'll be saving the people of Beacon Hills.
Kali and Aiden go to Derek's loft to kill him, but instead they find Lydia and Ethan. Jennifer drops in through the ceiling ready to fight. She takes on Kali and uses the broken glass from the ceiling windows as projectiles. She kills Kali and then turns on the twins, who have melded together. She breaks their neck, and leaves them for dead, then goes after Lydia and gets her to scream. The scream calls Derek and Cora back to the loft, so Jennifer can make her plea that if Derek joins with her she'll let the parents go. Derek agrees to help her. Scott sends her a video message showing where he and Deucalion are waiting for them: the abandoned distillery. Jennifer and Derek go to meet them there and start fighting Deucalion. He's more powerful than the both of them and easily tosses Derek aside. Duke then tries to make Scott kill Jennifer, which wastes more time. Scott manages to blind Duke with flash bombs, and then the lunar eclipse hits. Jennifer escapes and then returns in darach form. She's about to kill Deucalion when Derek stops her and reminds her that Deucalion has never seen what his alpha pack did to her. She heals his eyes so that he can see her ravaged face. Derek's plan worked; Jennifer used too much power in healing Deucalion and doesn't have enough left to kill him. She collapses against Derek, but he won't kill Duke either. Angered, Jennifer throttles Derek, but he's able to wait her out until the lunar eclipse ends. He tosses her away, and she puts up a mountain ash barrier to keep Scott from attacking. Scott pushes his way through the barrier, becoming an alpha. Jennifer is stunned. Scott orders her to stop the storm or he will kill her, even if it costs him the color of his eyes. Duke decides to save Scott the trouble and slashes Jennifer's throat instead. She escapes while they aren't looking and brings herself to the nemeton, hoping it will save her life a second time. Peter finds her there and kills her for good.