The episode opens with Scott taking dinner to his mom as she works at the hospital. While there he finds Danny, complaining of chest pains and having trouble breathing. Danny then throws up and Ethan, who brought him in, comments that the boy threw up mistletoe.

After Danny gets situated in a room and his breathing is stabilized, Scott goes to leave the hospital and Ethan follows him. Ethan tells Scott he knows he won't believe him, but he swears he didn't do anything to hurt Danny.

Scott isn't convinced, accusing Ethan of having an ulterior motive by pointing out that him and his brother set their sights on Danny and Lydia the second they got to Beacon Hills. Ethan promises that it wasn't their intention to hurt either of them, and that they only attached to them because they knew one of them was going to be important to "him".

After he says this a car pulls into the parking lot straight into another car, and when Scott looks inside he finds nothing but a single moth in the driver's seat.

—

Credits.

—

After the credits, Stiles and Noel are now there, standing with Scott as he talks to the sheriff. Scott informs him that two doctors have gone missing (the one that was driving the car and the attending ER physician).

The sheriff tells Melissa he wants to get her side of the story before he talks with the boys too much, so the three of them step away to let them talk.

"These are definitely sacrifices, right?" Scott asks, Stiles saying "That's one that Deaton mentioned. Healers."

"But what about Danny? He threw up mistletoe, that's not a coincidence. If he hadn't have been with Ethan, he probably would have died. Danny's not a healer," Scott says, trying to come to any conclusion.

Noel perks his head up a bit, knitting his eyebrows together and asking "Scott, did you hear that?" Scott turns to look at the sheriff where he's listening to his radio, and he turns to face Noel before nodding.

"What, what happened?" Stiles asks, and Noel tells him that the police found a body.

—

In the next scene Deucalion walks up to the scene with one of the twins (I honestly cannot tell them apart), and Chris Argent watches the twin tell him what's happening.

—

After that, at the loft, an alarm starts going off. Derek rushes to silence the alarm, Cora walking in and asking Derek what the symbol on the window means. Derek turns to see the alpha pack symbol painted on his window, and he tells her that it means the alphas are coming tonight.

—

The next morning Melissa sees Isaac and Scott watching over her in an adorable display, before they're both sent off to school and we cut to Harris's classroom. Jennifer is there, and she tells the students she'll be filling in for Harris since he's still missing.

Class gets started, and Stiles tells Scott that the body that was found the previous night wasn't strangled, but the man was killed by asphyxiation. Scott asks if the on-call doctor could still be alive, but Stiles says he doesn't know and that there have to be at least twenty other doctors in that hospital that could be next.

Scott then gets a call from Deaton, who tells him he's the one that's going to be taken next. Scott asks him what's happening in disbelief as we see Deaton being swarmed by moths like the doctor was in her car.

—

After the break it's back at the loft, and Boyd and Isaac enter as Derek immediately tells them to go back to school. Isaac tells him they can't, because they are "very very incredibly sick."

"With what, brain damage?" Derek asks jokingly, Isaac dismissing that with the explanation that he has a migraine and Boyd has explosive diarrhea (which is obviously an embarrassing coverup judging by the boy's expression).

"We're here to protect you," Boyd says, Derek repeating that in disbelief. "I'm in trouble then," he jokes, but Isaac defends that Boyd has a plan that involves the electrical currents they had to endure when they were in Gerard's basement in season two. He then reaches in his bag and pulls out a hose.

—

After Scott goes to the clinic and finds Deaton missing, we're back at Derek's, where Boyd starts running water all over the floor of the loft and talking about how much energy it would take to kill a human when mixed with water.

He suggests that if they can rewire the power to run into the water, that anyone that steps in would get a "shocking surprise." Derek seems impressed (or at least enthused) and he asks out of nowhere "Well, what does Noel think of this plan?"

Isaac and Boyd look confused, but of course, Noel then steps into the loft from where he was previously unseen with his hands in his pockets. Boyd and Isaac shoot looks at each other, both wondering how they didn't sense Noel's presence themselves or know that he was following them.

"I think it's great. Not as great as a simple text telling me that you're alive, or maybe a phone call, but it's great," he says, smirking to himself and not breaking eye contact with Derek.

"Can we keep the civil disputes to a minimum right now? It's not the time to act like an old married couple," Isaac says to Noel and Derek, who are staring accusingly at each other. The tension could be cut with a knife as the scene changes to go back to the clinic, where Scott and Stiles are.

—

After Scott and Stiles debate whether or not to tell the sheriff about werewolves, they run into Morrell who tells them they have to get help from someone who can communicate with the supernatural to find Deaton.

Scott asks if she means Noel, because of his connection to Laura, but she says "Not benevolent guides like Laura Hale, real creatures. The malicious side of the supernatural."

Stiles knows who she's implying, and tells Scott that she means Lydia.

—

After a whole lot of mumbo jumbo (in which Lydia fails to perform and doesn't help Stiles and Cora find Deaton, Scott is told by Deucalion that either Derek or Deaton will die tonight, the teens go out on the search for Danny to see if he has any information, and the sheriff and Melissa figure out that the latest sacrifices are dying because they're being suspended and are unable to breathe freely) we finally come back to the loft with Derek, Isaac, Boyd, and Noel.

Boyd hits the lights in the loft to spark the electricity, then throws a wire into the water as it cracks and sparks.

"Is this gonna kill him?" Isaac asks warily from where he stands with Noel and Derek, Boyd staring at the water on the floor and saying that he hopes so.

—

Scott and Allison have a scene where they find out that Chris's map has the potential locations of where the next six sacrifices will be found, after which we're at the hospital with Stiles and Danny.

Stiles snoops in Danny's backpack and convinces him that he's dreaming, finding a report he's writing on some kind of current. Scott recognizes the word, and after he does, we're in the loft with the boys and Derek.

Boyd and Isaac sit on their own, while Noel and Derek stand together on one space above the water.

Isaac looks across the room and asks if the light switch across the loft is supposed to be on, Derek looking across and saying angrily "Yeah."

"What does it mean if it's not?" Isaac asks, and Derek elaborates "Someone cut the auxiliary power."

"What about the main-" Noel starts to ask, but suddenly all the lights go out and the three teens scramble to their feet.

Derek looks out and steps into the water, and doesn't get a single shock, showing them that their plan has failed. Noel watches Derek step out into the middle of the loft and calls out his name, almost as a warning.

Derek doesn't respond, and Isaac asks from where he stands (now behind Noel, who is in the water) what they do now.

The camera pans in on Derek, as his eyes begin to glow red. "We fight," he says surely, as we cut to black.

—

After the break, slamming is heard on the door of the loft before the door is thrust open. Kali stands in the doorway, looking at the four boys who stand together in the middle of the loft.

"I'm gonna be honest, Derek," she says as she steps in, claws brandished. "When Ennis died, I thought to myself, 'I'll just go for it'. I was going to find you, and kill you, wherever you stood. Then I remembered, how you surround yourself with these teenagers, hiding behind them. And I thought, 'what's a girl gotta do to get you alone'?"

Suddenly behind her, the twins walk in, holding Jennifer by her wrists and neck. She looks horrified, looking to Derek who stares at Kali angrily.

"You and me, Derek, or they tear her apart. What do you say? Think you can beat me one on one?" Kali asks, and Derek gestures for the boys to step aside. Noel stands firm longer than Isaac and Boyd do, Kali grinning at him, and in doing so displaying her fangs proudly.

"So devastatingly loyal, Noel Whittemore," she says almost adoringly, taking a step closer. Derek does the same, effectively stepping slightly to the side as he does to put himself between Kali and Noel.

She laughs, shaking her head and saying "It's a pity, it really is. You and I, we could have been great friends. I can feel it."

"Noel. Go," Derek commands, not taking his eyes off Kali. Jennifer looks at Noel in confusion, trying to find her student's face through the warped structure of his wolf form. Before she gets the chance, Noel obediently steps away and joins Isaac and Boyd, never taking his eyes off Kali.

The two alphas then attack each other, Derek giving her the same threat he gave Stiles in season one (that he's going to rip her throat out with his teeth).

Upon their first shot of contact, we cut to the clinic, where Stiles, Scott, Lydia, and Cora are trying to find Deaton and how that relates to Danny's essay for Harris's class.

—

Cora deduces that Deaton is in the same vault she and Boyd were kept in, and she proves to be correct. But she also gets a text, saying "It's Noel. The plan didn't work. They cut the power."

Scott tells them that he'll go find Deaton, and that the rest of them need to get to the loft as quickly as possible.

—

Kali and Derek continue to battle in the loft as Jennifer sobs, and at one point when Kali gets the upper hand, she and Noel call out his name in unison. Derek recovers fairly quickly, but is again overpowered.

Meanwhile, Scott finds Deaton in the vault, but is met with his boss hanging by his wrists surrounded by a ring of mountain ash.

Derek continues to fight Kali, and Noel moves to make a mad dash for Jennifer as she screams. Derek tells him not to, and he stops Isaac and Boyd from following behind him.

Derek keeps fighting to the best of his ability, but it's evident that he's no match for the more experienced alpha. And speaking of alpha, Scott tries in vain to break the mountain ash barrier as his eyes turn from yellow to alpha red. He doesn't succeed, however, and the sheriff bursts in to shoot Deaton down with a single blow.

In the building of Derek's loft, Cora, Stiles, and Lydia start to turn all the power switches back on. Noel and Isaac dive across the water before it ignites and grab Jennifer, the two of them holding her safely out of the water, but Boyd falling inside. The three of them (Boyd, Derek, and Kali) are electrocuted, but the effects seemingly don't last or aren't powerful enough.

Kali orders the twins to get Derek, and they run into the water to do so. The twins grab Derek as Kali grabs Boyd, Noel standing up as the twins hold up Derek's arms.

"What are you doing, stop!" he yells, starting to rush in to help, Before he can get anywhere close to being able to help, Kali picks Boyd up and slams him down onto Derek's waiting claws.

Boyd starts to choke on his own blood, and Noel stands in the water breathing heavily and staring in absolute terror. Even the twins appear remorseful, as Kali lets Boyd go and the boy lowers down to his knees as he lets out moans of pain.

She steps away from the two and looks to the twins, who follow her as she says "I'm giving you to the next full moon, Derek. Make the smart choice and join the pack. Or next time I'm killing all of you."

Noel doesn't even acknowledge her as she walks past him, eyes streaming tears as he stares at Boyd. Derek picks Boyd's head up from where it rests on his shoulder, speaking soothingly to him and trying to stop the bleeding. Boyd breathes out that it's okay, Derek arguing that it's not and trying to keep him stable.

Boyd repeats that it's okay, and the two finally make eye contact. Derek just stares at him in disbelief and apologizes, Boyd saying shakily "The full moon... That feeling? It was worth it. Did you know that it was the lunar eclipse? I always wondered... What that felt like, for one of us. For a werewolf."

We suddenly see Erica, in the bank vault, asking Boyd what he thinks the lunar eclipse will be like since it's just the earth's shadow. She suggests that it might make them stronger, and that she hopes it will.

We then see Kali turn to face Erica, as the girl attacks her. Boyd then falls to the ground from where he was slumped against Derek, finally gone, and we see Erica in his memories calling his name and reaching for him as she passes.

Derek kneels in the water, watching Boyd on the ground, and Noel finally closes the gap and stands behind Derek as Cora sobs over Boyd's body. Noel's hand slowly reaches out and grips tight to Derek's shoulder, tears falling from his eyes as Stiles watches and Lydia runs in to survey the damage.

The episode ends with Chris demanding that Gerard tell him the truth about everything, and Allison coming in to confront him as well.

Deaton then explains to Scott what a true alpha is, and that he is one, and the episode ends on that revelation.