Cora is Derek's younger sister and was in the Hale House when it was set alive. Prior to the Hale House fire, Cora fled to South America where she stayed until she heard about a new alpha in Beacon Hills, her brother and went back to Beacon Hills. 
Cora is being held in a bank vault, Derek breaks in to save Boyd and recognizes the brunette as "Cora", and seems oddly vulnerable upon recognizing her. Morell closes the mountain ash circle around the vault and the wolves shift, finally able to feel the moon. It’s revealed that Cora is Derek’s younger sister who was presumed dead. Allison watches the fight, shocked, before breaking the mountain ash seal on the vault against Derek’s warning, and both Boyd and Cora run out. 
In the woods, Cora approaches a girl, but then Isaac appears and attacks Cora. Scott and Derek appear as backup, and Cora runs, with Derek and Isaac right behind her. Boyd and Cora approach the school, and seeing Derek they decided to go over the school instead. Allison has brought arrows with flashes on them and uses them to get Boyd and Cora into the building. Derek and Scott use themselves as bait to get Cora and Boyd into the boiler room. They spray fire extinguishers, hoping to confuse them before sprinting out of the boiler room and locking the door, unaware that there is another person inside with them. Cora and Boyd approach the teacher, who is getting supplies. Derek comes back into the room and attacks them before they can do anything to her. Derek stays in his human form and manages to hold them off, but they tear him apart, and he seems to pass out. Derek is worn out and torn up, but alive, and both Boyd and Cora are passed out at his feet. 
Cora Hale works out in the loft with Derek watching. She’s struggling, and Derek tells her to stop as she’s not done healing, but Cora wants to fight back as soon as possible. Derek kicks her hand out from under her while she’s doing push ups, and Cora is furious saying, "I came back for this? I can't believe I got my ass locked up in a vault for three months for you." Derek tells her he’s sorry to disappoint her before the proximity alarm goes off and the alphas, minus the twins, appear. Cora immediately goes into fight mode, but she’s not at full strength yet, and the former Nurse from the hospital immediately delivers a blow that would have been lethal to a human by throwing her to the ground where her head slams against Derek’s concrete flooring. The female Alpha pulls a pipe from the loft’s exposed industrial system and fights Derek with it before putting it through his torso. Deucalion tries to talk to Derek as the female alpha, Kali, twists the pipe through his back. The other alpha lets Cora up, but she knows better than to try to rush to him at this point. Derek’s condition is beginning to visibly worsen as Deucalion continues his discussion of the alpha pack. Cora is beginning to look very worried. Deucalion shares that when an alpha kills one of their betas they absorb the beta’s power. Apparently Deucalion found this out accidentally, but ended up killing all his betas once he realized. Deucalion remarks that Derek looks like his mom before beginning a rant that he is the “Alpha of Alphas”, the “Apex of Apexes”, the “Predator of Predators”, “Death, Destroyer of Worlds”, and “The Demon Wolf,” complemented by dramatic lightning although there is no evidence of a storm happening. As his rant culminates Deucalion’s sunglasses shatter. Kali pulls the pole out of Derek’s back, and the alphas leave as Cora rushes over to her brother. LAter at night, it is now raining, and Derek is staring out the window. Apparently he’s told Isaac that he needs to leave. Isaac doesn’t know where to go, and when he keeps pushing Derek throws his empty water glass at him. Muscle memory serves Isaac well and he ducks and covers well before the glass shatters, but that’s enough to get him out of the loft. Cora is seen hiding just around the corner and listening to the conversation, looking stressed. 
Peter, Derek, Scott and Cora are planning the fight in the loft. Scott doesn’t like the plan to just go kill everyone, and Peter makes a smart comment while Cora asks why “this kid” is necessary at all. Derek points out that Scott helped to save Cora’s life. When Scott says that there’s no way to kill that many alphas, Cora corrects that they’re only trying to kill one, Deucalion. Peter compares the pack to a hydra, a mythological monster with multiple heads that would grow two new heads for everyone one that was cut off, to suggest that this plan my backfire. At the mall, Scott and Isaac walk into the mall where Deucalion has already arrived. Derek is already there and shifted. It’s revealed that the rest of the alpha pack is also at the warehouse, but so are Boyd and Cora. Derek makes the first move by running at Deucalion before being intercepted by Kali. Boyd takes on Ennis while Isaac goes for the twins in their combined form. Deucalion simply watches as his pack takes on the Hale pack and Scott is shown receiving the torso wound that Allison had to stitch up. The alpha pack brings the fight to a stand still, and Deucalion delivers the ultimatum that Derek must kill Boyd, but the others will be let go. Derek hesitates, and Kali tells him that he must choose between pack or family while shifting her position on top of Cora, making the bones in Cora’s neck creak. As Derek struggles to make a decision, Allison appears with flashing arrows. The arrows cause enough confusion for both Cora and Boyd to get up. Scott rushes at Ennis. Derek and Ennis begin to fight. Scott claws at Ennis’s calf, the only thing he can reach, and Ennis stumbles, which is the movement that causes both him and Derek to pitch off the platform.  Cora is investigating an escalator, the same one that Derek and Ennis fell onto, when Peter shows up. Neither trusts the other, and it is revealed that both bodies are gone. Later, Peter and Cora arrive at the Animal Clinic. Peter realizes that the entire alpha pack is at the clinic. Cora wonders who’s actually in the clinic before Aiden and Kali exit the clinic. Kali roars while held back by Aiden, and Peter comments that that probably wasn’t for Derek and they flee. 
The alarm at Derek's apartment goes off. Cora asks him what it means. The Alpha Pack put the their symbol on his window. He tells her it means they're coming, tonight. At the school, Cora pulls the fire alarm and stands outside coach's office where Lydia and Aiden are inside. Aiden leaves and then enters in Cora. Cora tells Lydia to stop hanging around Aiden. Lydia tells Cora that that won't be happening; she can handle a werewolf. Cora grabs Lydia's arm, and when Lydia asks her to let go. She doesn't comply, but Stiles shows up, and he tells her to let go. Stiles pulls out a Ouija board and asks Lydia to try it. Lydia tells him it's a shot in a dark, but he's adamant about trying it for Deaton. All three of them, Cora included, put their hands on the board and then nothing happens. When Cora and Stiles both look at Lydia, she says she doesn't know where Deaton is. Cora, Stiles, and Lydia are headed to the hospital to get Danny. Scott says he will meet them there. When Stiles asks why, Scott shows him a text from Allison claiming she found something. Scott, Stiles, Lydia, and Cora have met up at the Animal Clinic. They’re going over Danny’s paper and find a map of the telluric currents that run through the ground of Beacon Hills. Learning that Harris wrote a note on the paper saying Danny should not pursue the research, Scott realizes that the teacher knew something was going on. Stiles also points out that Beacon Hills has a high number of the currents flowing through it making it an actual “beacon” of energy. When they combine Danny’s map with Chris Argent’s map they find likely locations for the future body dumps and figure Deaton is being held somewhere along the telluric current that runs between where he was taken and where his body will be found. Cora realizes the bank where she and Boyd were held is on that current’s path. Cora gets a text from Boyd who explains that the plan didn't work because the alphas cut the power. The group decides to split up, with Stiles, Cora, and Lydia going to the loft to help Derek while Scott heads to the bank to find Deaton. Stiles, Cora, and Lydia arrive at the loft where Derek has been holding his own in hand to hand combat with Kali. Stiles, Cora, and Lydia head to the electrical room and begin flipping all the switches. Boyd dies. Stiles and Cora rush in. Derek seems stunned. His hands are shaking. Cora runs to Boyd, weeping, while Stiles places his hand on Derek’s shoulder to comfort him. Lydia, Isaac, and Jennifer can only watch, stunned. 
Cora and Stiles are talking about what happened to Derek when he was younger. She says that Peter and Derek were in the cellar for two days. She stares out the window of Derek's loft at the rain, which slowly washes the alpha pack symbol away. Stiles asks her if two days is standard or if Derek can be expected to be gone for longer. Cora asks Stiles why he cares. Stiles explains that over the last few weeks Scott tried to kill himself, Deaton nearly got ritually sacrificed, a girl that he's known since he was 3 was ritually sacrificed, Boyd was killed by alphas... he asks her if she wants him to keep going. Cora asks if Stiles thinks Derek can do anything about any of these things, and Stiles replies that since everyone seems to be after Derek maybe he's the one who should be doing something about it. Cora tells him that there's something different about Derek now. "He wasn't like this when I knew him." Stiles asks what Derek was like, and Peter comes down the spiral staircase of the loft. "A lot like Scott, actually." He further claims that Derek was a lot like most teenagers, unbearably romantic, profoundly narcississtic, tolerable really only to other teenagers. Stiles asks what changed him. Peter tells him that it was a girl, and Stiles in incredulous that Derek "is the way he is" because he heart broken. Derek met Paige when he was a sophomore. Stiles asks Peter how old Derek was back then. And how old Peter was. And then how old Peter is now. "Not as young as we could have been but not as old as you might think." Stiles asks Cora how old she is, and she replies 17 "how you'd measure in years." Stiles decides to drop the subject. He asks Peter to go on with the story. Peter tells him they were teenagers, they went from I Hate You to frantic groping in any dark corner they could manage to find themselves alone in for five minutes. Their favorite dark corner was an abandoned distillery outside of Beacon Hills. Peter traces a spiral on the fog of the window. Stiles comments that werewolves take revenge to a whole new level. Cora tells him that it's not just revenge, because losing a pack member is like losing a limb. Peter comments that Ennis wasn't even allowed to see the body. Cora explains to Stiles that the emissaries keep them connected to humanity, but they're also a secret from most of the pack. Derek, Cora, and Peter didn't know about Deaton or Morrell. Stiles gets upset that no one told him that their guidance counselor was working for the alpha pack, because he shared intimate details with her. Cora asks if she gave him good advice, and Stiles admits that actually she did. This is what Deaton used to do for Talia. Cora asks Peter why he would choose Ennis to bite Paige. He explains that Ennis needed a new member for his pack and doing a favor for Talia's son would get him in good with her. Everyone wanted to be in good with Talia. Cora asks Peter if Paige turned. He says that she should have, because most of the time it takes. "When you offered it to me, you said if it doesn't kill you," Stiles replies. Peter says he took Paige's body from Derek and placed her in the woods where he knew she would be found. Cora asks what happened to Derek. Peter explains that taking an innocent life takes something from you, a bit of your soul. It dims the once brilliant golden yellow of their eyes to a cold, steel blue. Cora and Stiles sit together in the loft. She asks him what he's thinking about. There's a look on Stiles's face that make her want to punch him. Stiles says he doesn't believe Peter. He says that in Ms. Blake's class they're reading Heart of Darkness which is told in first person by Marlow, who is an unreliable narrator. You know the details have changed just because of his perspective. Stiles doesn't think they got the whole story. Cora asks if he's just going to ask Derek about killing Paige. "If I have to... yeah." 
At the school, Cora draws a spiral on the back of the door. Aiden opens the door to the office and calls Derek out. Lydia threatens to scream. "You wanna fight, Derek, come and get me!" Aiden says. Cora attacks him from the side. Aiden roars at Cora and grabs her by the throat. He throws her across the locker room, and then picks up a weight from the bench press. Lydia begs him to stop, but he beats Cora on the head with the weight. He's about to hit her again, but Scott and Ethan stop him. "Aiden! You can't do this!" "She came at me!" "It doesn't matter! Kali gave Derek until the next full moon. You can't touch him or her." Aiden looks at Lydia, and he stops resisting. Ethan nods at Scott and takes his brother away. Stiles thinks Cora's hurt worse than she looks. Cora cleans out her wound while Scott, Stiles, and Lydia watch. She tells them all that she'll heal and tries to stand up straight, but she wobbles and Scott catches her. "Do you realize how suicidally crazy that was?" Stiles asks her. Cora replies that she did it for Boyd because none of them were doing anything. "We're trying," Scott tells her. "And you're failing. You're just a bunch of stupid teenagers, running around thinking that you can stop people from getting killed. But all you do is show up late. All you really do is find the bodies." Stiles is driving Cora home. "Stiles, you have to tell you dad," Allison says. "Tell him whatever you need, but you have to get him to believe." Stiles agrees and tells Cora that he's going to need her help. Stiles is in his room with his father and Cora. He paces back and forth, unable to figure out how to start talking. He eventually starts but his father doesnt belive him. Stiles gestures Cora to show him what she is but she collapses on the floor. They call an ambulance to take her to the hospital. Derek is at the hospital holding Cora's hand. She comes around and says his name. "'What's happening to me?" "I don't know. But I'm not leaving, okay? Not again." He kisses her forehead. 
The hospital is being evacuated. Peter is in Cora's room, wiping her brow. He turns and shout, "Hey, anyone wanna tell me when they're getting my niece out of here?" Melissa walks in, apologizing, and stops dead when she sees Peter. "You're supposed to be dead," she says. "I get that a lot, actually," he replies. Cora jerks away and throws up black ooze. She is then moved. Stiles sees Cora lying on the ground behind the combatants and pulls Peter to his feet. While the big guy holds Scott against a wall by his throat, Stiles and Peter slip by to help Cora. "Ethan, Aiden, stop! You don't know what you're doing!" Scott says. "All we want is her," they reply. Derek and the alpha twins turn to see Jennifer escaping down the elevator. Peter carries Cora over his shoulder as they all run. Peter, Stiles, Scott, and Derek head into an exam room. Peter puts Cora down on a gurney. She is then taken to the ambulance where she waits with Stiles. She dies and Stiles has to do mouth to mouth to revive her. He succeeds. Later, Isaac pulls up to the ambulance, and Peter and Stiles transfer Cora to Isaac's car. 
Cora is in the back seat of Isaac's car with Peter. After they get the Argent's involved, Cora gets tranfered to the back of Chris' car. She is then taken back to Derek's loft. Cora gasps for breath and coughs, as Derek looks on, worried. Isaac asks if she's dying. "I don't know." Isaac asks him what he's going to do, but he doesn't know that either. Isaac asks if he wants to figure it out, "Because while Scott and Stiles were out there trying to help people from being killed, you were in here, rolling around the sheets with the actual killer." He asks if Derek gets how many people are dead now. Erica and Boyd are dead and Cora is dying, "and you are doing nothing!" The next morning, Derek sits on the bed next to Cora and siphons some more of her pain. Derek sits at Cora's beside, looking worried. She coughs. Derek tells Peter that he's got to do it now. Derek brushes Cora's hair from her face. He takes her hand in his and draws out her pain with both hands. His eyes flash red, and he cries out in pain. As he roars, his eyes go from red to blue. 
Cora gives Derek a drink of water as she pets the back of his neck. He's weak and looks at her in surprise. "You're okay." She tells him that she's doing a lot better than he is right now because of him. Peter gripes that he hopes it wasn't for nothing. The moon is rising and he drained himself all the way to the red, while there's a fully charged alpha on her way to rip him apart. Ethan tells Derek that they know about the lunar eclipse and that Kali isn't going to wait around for it to level the playing field. She's coming and bringing Aiden with her. Peter is convinced that they should go. "You want me to run?" Derek asks Peter. "No. I want you to stay and get slaughtered by an alpha with a psychotic foot fetish. OF course I want you to run." Cora adds that if Derek wants to fight and die for something, he should do it for something meaningful. Derek asks them how they know he's going to lose. "We don't. But I bet she has an idea," Peter replies, and gives a meaningful look at Lydia. Peter asks her what she feels. "I feel like I'm standing in a graveyard." Derek and Cora get into Derek's truck. Peter tells them not to call until they're at least 100 miles away. Derek doesn't look pleased, but he drives off. While in the car they hear Lydia screen, Derek pulls over "What the hell was that?" Cora asks him. He gives her a panicked look. "Lydia. We have to go back." Derek and Cora head back to the loft. Cora comforts Lydia while Derek faces Jennifer. "You did this for me?" "For us. For anyone who's ever been their victim." Derek yells at her to stop talking like a politician. She then asks him to think about someone else's cause: Scott's. Jennifer needs a guardian. If Derek chooses to go with her, he can fill that role instead of the parents she took. Cora warns Derek not to trust her. Cora and Lydia get up to leave. Cora says they need to find help, even though they don't know from who. As they're leaving, they hear a sound behind them and the twins separate. Cora realizes that they're alive. Cora and Lydia bring the twins to the Animal Clinic. They put each one on a table, and Lydia takes Aiden's hand. Cora asks Deaton if he can save them, but he has they have to start healing on their own. The next day, Cora helps Ethan to his feet, and Aiden tells Lydia that he knew that she cared about him. Derek and Cora leave the loft to go back to South America. 
- "Chaos Rising"
- "The Girl Who Knew Too Much"
- "The Overlooked"
- "Alpha Pact
- "Lunar Ellipse"