Melissa McCall is the head nurse in charge and is ushering the patients to their different places when Scott McCall enters bringing his mother dinner, much to her delight. She reports that the patients are all the result of a 10 car pile up and that the ER attending is not answering his pages. She then asks for more on the on call Dr. Hilyard who is 10 minutes away. A women walks up and asks for something for the pain. Melissa turns her away as giving her something could complicate things. Scott then goes to the women and explains that he read somewhere on the internet that human contact can help with the pain. Using his werewolf powers he touches the women lessening the pain. Enter an alpha twin Ethan carrying Danny Mahealani yelling for help. Danny is visibly sick. Switch scenes to the on call doctor Dr. Hilyard at 9:45 who says that she may be more then 10 minutes away because of the car pile up, the very reason they need her. Melissa moves Danny over to a chair where Scott questions Ethan on what he did to Danny. Ethan claims he did nothing, but Danny was complaning about not being able to breathe and then it got worse. Danny then throws up a mysterious substance: mistletoe. Back to Dr. Hilyard who is growing more impatient stuck in traffic, when a moth lands on her car window. One then comes through the air conditioner. Melissa tells the boys that she thinks Danny is suffering from Tension Pneumothorax, which is when the lung is punctured and air escapes into the chest cavity causing a pressure build up against the heart and difficulty breathing. She also explains that his “Larynx has shifted to the side.”
Back in Dr. Hilyard's car more and more moths come through the air conditioner. They swarm the doctor and she spins into oncoming traffic. When she looks into her rear view window, she sees a face. The Darach. Scott and Ethan both seem close to panic as Danny is wheeled into an exam room. Melissa further explains that Danny’s heart is being pushed up against his chest cavity. Fearing he might die due to the lack of a doctor, Melissa takes out a large syringe. Danny stops breathing, and she jabs the syringe into his left pectoral in what appears to be a procedure called a “needle thoracostomy.” Once inserted, needle has a valve that is opened to allow the air to escape and relieve the pressure in his chest. Danny begins to breathe normally. Danny gasps out “Thank you.” Scott says the whole thing was “awesome,” but Melissa counters that it was no big deal.
Scott and Ethan walk outside. Ethan says he didn't do it and tells Scott that the twins were tying to find the person most important to Scott. It wasn't Danny but Lydia. A car rolls into the parking lot. It's Dr. Hilyard's car, and it's empty. A dead and dried moth sits on the seat. The police arrive. While Sheriff Stilinski takes Melissa’s statement about the two missing doctors, Stiles and Scott work out that these latest disappearances are definitely part of the Darach sacrifices. Stiles remembers that Deaton mentioned healers as one of the groups of three that might be targets. They are confused as to why Danny was fed mistletoe, since it doesn't fit the pattern. Cut to the crime scene, Deucalion is with one of the alpha twins. The alpha twin speaks into the Demon Wolf's ear perhaps telling him what's going on. Chris Argent stands in the background watching them.
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.
Melissa is sleeping and wakes up to see Isaac and Scott sleeping at the foot of her bed. Apparently while making sure she wasn't the third sacrifice, the boys fell asleep. The boys argue about who was on watch last. Melissa says she's not a doctor, so the boys need to go to school.
Jennifer Blake is filling in for Mr. Harris who is still missing, she means sick. Stiles tells Scott that the ER doctor wasn't strangled but still died from lack of air. They just don't know how. They wonder if the on-call doctor could still be alive. Deaton calls Scott and tells him that he is the third sacrifice. Moths surround the animal clinic.
The door opens to Derek's loft. Derek tells them to go to school but Boyd and Isaac have a plan. Boyd says that when Gerard had Erica and him locked up, he used electrical currents to incapacitate them, so they should do something similar.
Meanwhile at the clinic, Deaton is missing and the Sheriff wants to know everything.
Boyd is flooding Derek's loft and talking about how they can use the currents to their advantage to take down Kali. He explains that, in a pool of electrified water, it would take up to 50 milliamps to kill a normal human. That is less than the power it takes to turn on a light bulb. He plans to disable the circuit interrupter in the building’s electrical room so that the current will keep flowing through the flooded loft. He says it will give Kali a shocking surprise.
Back at the animal clinic, Scott tells the Sheriff all he can without revealing his secret. Then he tells Stiles they need to tell the Sheriff. Stiles argues against it, but Scott convinces him that that's the right plan. However, Marin Morell has shown up to ask the Sheriff to help find her brother. She then walks up to the boys and tells them that no sheriff or deputy can help find her brother. She's going to help them. She tells them Lydia can help them find him,
At the school, Lydia and Aiden are getting it on in Coach's office when the fire alarm goes off. Lydia gets her things together to go, and Aiden asks where she's going. She'd like not to die, thank you. She tells him to go first, and he leaves and then enters in Cora.
Meanwhile at the hospital, Melissa stops the Sheriff as he escorts a body inside. She asks "Is it Doctor Hilyard?" and he nods. She then questions him about the marks on the body, and when it's revealed she wasn't strangled, Melissa asks him to come look at the other bodies with her because she may know how the other doctor died and it may help them find Deaton.
Back at the school, 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. Scott's in the hallway, and Stiles texts him to say he's found Lydia. He hears the sound of a steady tapping and follows it.
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.
Scott continues to follow the beating sound and enters the music room where Deucalion sits hitting a piano. He changes beat when Scott enters. Duke asks Scott if he knows what a metronome is. He doesn't wait for an answer before telling Scott it's an instrument to keep rhythm. He tells Scott that the tempo in his life has sped up the last couple of hours. Duke offers to help Scott find Deaton.
Back in the lab, Stiles is trying something else with Lydia. He wants to try psychometry. Lydia claims she's not a psychic, but Stiles asks her to try it anyway because she's something. The keys are cold, but that's all she knows.
Scott is angry, and Duke offers Scott a challenge. If he can get the cane away from him, Duke will tell him where Deaton is. Scott puts up a fight, but Deucalion then slashes him with the blade hidden in the tip of his cane and explains that he is not behind the rash of ritual murders, saying he’s not the one praying to ancient gods or gathering herbs or “whatever the hell druids are supposed to do." Deucalion admits he is part of the pack that wants Derek dead and that Kali is coming for him. He says Scott will have a difficult choice to make. Someone is going to die, Derek or Deaton, and the decision is up to Scott. Deucalion leaves him with a cryptic clue: "Let the currents guide you."
Back in the lab, Stiles wants to try automatic writing. Lydia then proceeds to draw a tree. Stiles gets frustrated, and Lydia says she's a genius yes, psychic no. She then tells them that it's not her they want. It's Danny. When Stiles asks why, Scott enters and tells them Danny was a target but not a sacrifice.
At the hospital morgue Melissa pulls out the body of the ER doctor. She explains that even without the marks of strangling, both doctors still suffocated. She points out the marks on the arms, which mean that he was tied up, but the marks are too deep to be from struggling to get out. She thinks he was suspended. A person suspended from the ceiling by their hands will eventually suffocate. They would have to keep pulling themselves up in order to take a breath and after a while would no longer be able to. The Sheriff asks how long would they have once they stop struggling to lift themselves up. "Minutes," she says.
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.
Back at the loft, Boyd flips the switch and throws the wire with the current into the water. He, Derek, and Isaac are all on boards to keep them above the water line. Isaac asks if it will kill the alphas, and Boyd says he hopes so.
Allison was looking through her father's things when she found a black light. The elevator dings before she can explain what it is. Her father, Chris Argent's, arrived. She herds Scott into her closet. She motions for him to stay quiet, and he nods. Chris looks at a map on his desk and points to a place, nodding. He then looks visibly shaken. Back in the closet, Scott gets an erection. Allison orders him to stop, but he says he can't. Allison turns around, trying to help the situation but, but Scott tells her "That's worse." She smiles and giggles turning back around. The two of them almost kiss when Scott stumbles back, afraid the noise will arouse Chris's suspicion. They hear a door close and exit the closet. They enter Chris's office, and Allison brings Scott over to the map. She explains that Chris tried to cover it last time she was here. Scott doesn't see anything until she holds the black light over it. Chris has been tracking and marking everything, the Darach's kills, Cora and Boyd's lock up, the alpha fight. There are more marks on the map than there are sacrifices. She thinks that Chris knows where the bodies are going to be found. Chris comes back up in the elevator and looks in the various rooms. Scott escapes from behind him.
At the hospital Stiles enters Danny's room. He asks Danny if he's awake and then proceeds to slap him slightly awake. Danny goes back to sleep, and then Stiles goes into his bag. Danny asks him what is he doing, and Stiles tells him that this is all a dream. Danny wonders why would he dream about Stiles going through his stuff. Stiles tells him to take responsibility for his dream. He then pulls a paper out of the bag that Danny did for Harris.
Scott tells Stiles that Deaton might be at one of the six locations, but they're all over town and he can't get to them fast enough. Stiles tells him that Danny's paper on the telluric currents might have found something.
Back at the loft things are going from bad to worse, as Isaac points out that Derek's alarm system is off. Then the lights go out. Derek steps in the water and proves that there plan to use the currents will not work. Isaac asks Derek what they are going to do now, he answers with "We fight." The door to his loft opens up after ominous clanking to reveal a very angry barefooted alpha that goes by the name Kali. She says when Ennis died, she initially thought to simply find Derek and kill him where he stood, but then she remembered how Derek surrounds himself with teenagers “hiding behind them." She wondered what she would have to do to get him alone and decided that kidnapping and threatening Ms. Blake might work. Derek agrees, motioning to Boyd and Isaac to get back so he can fight Kali one on one. Derek says his iconic one liner. "I'm going to rip your throat out with my teeth." And then he and Kali begin to fight.
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.
Derek and Kali fight through the water. The trio drives on. Scott drives troward the bank.
Scott arrives at the bank vault where Deaton is suspended by his arms. He hangs limply. Scott rushes forward but is shoved backward with a flash of light. He realizes that Deaton is surrounded by a circle of mountain ash.
Stiles, Cora, and Lydia arrive at the loft where Derek has been holding his own in hand to hand combat with Kali.
Scott tries again to penetrate the force field, pushing against it with all his might and filling the room with a blue glow. His eyes shine yellow then red as he pushes harder and harder, but the barrier will not bend, and Scott is thrown back to the floor. He looks on helplessly as Deaton hangs there. Sheriff Stilinski is suddenly in the doorway of the vault, gun in hand. He fires at the rope, and Deaton drops to the ground.
Stiles, Cora, and Lydia head to the electrical room and begin flipping all the switches. Stiles texts Isaac to explain that they’re there and are about to turn the power back on. Isaac rushes to protect Ms. Blake, while Boyd is thrown into the fray by the surging current. Kali and Derek both go down from the shock. Kali is the first to recover and orders the twins to grab Derek and hold him while she lifts Boyd up and drops him onto Derek’s claws.
Boyd is impaled on Derek’s claws. Derek’s eyes glow a bit brighter red, and Boyd gasps in pain. As she exits, Kali gives Derek an ultimatum – join the alpha pack by the next full moon or she will kill all of Derek's Pack next time. As the twins follow her out, Ethan seems slightly remorseful. Derek applies pressure to Boyd’s wounds, trying in vain to stop the bleeding. Derek apologizes, but Boyd says it’s okay. He says the feeling he got on the full moon was worth it. He then begins talking about a lunar eclipse and what that might feel like for a Werewolf. Just before his death, Boyd remembers Erica supposing that an eclipse might make them stronger. She then attacks Kali and is killed. 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.
Meanwhile, in Gerard's room, Chris demands to know the truth about Deucalion. After Chris leaves, Allison shows up. Gerard says he’s not surprised to see her but is surprised that it took her so long to visit.
The Sheriff explains to Scott and Deaton that he figured out where Deaton was because one of the Celtic symbols on one of the vials at the vet clinic reminded him of the bank’s logo. Deaton tells Scott about his eyes changing colors. He says Scott is a “True Alpha” one who rises on strength of character and sheer force of will as opposed to those who take the status from another alpha. Deaton says it's rare, happening only once in a hundred years but that he believed Scott had this potential in him since he was first bitten. Scott realizes that this status is what Deucalion has been after: a True Alpha. He realizes that he is the target instead of Derek.