As the episode starts, we see Scott laying in bed at night as he gets a call from Stiles. All he hears is static and heavy breathing, as Stiles says he doesn't know where he is or how he got there.

Scott tries to reassure him, asking if he can see anything. Stiles says he can't see in the dark, and that there's something wrong as the line suddenly dies.

Scott calls back, but keeps getting Stiles' voicemail, until Stiles calls him back himself. He says he doesn't think he can get out of wherever he is, because he can't move, as Scott asks again where he is.

Stiles says he thinks his leg is stuck and bleeding, and that there's a horrible smell that's making his eyes water.

Scott offers to call Stiles' dad, but Stiles begs him not to, saying he already worries enough about him. Stiles begs him not to call his dad and pleads with Scott to come and find him without letting his dad know, saying he'll call right back before hanging up. Scott begs Stiles not to hang up, but he does anyway, and Scott is left standing there shaken.

We see him back on the phone as he turns the lamp on in an abrupt jump cut, saying "Just please, get to Stiles' house, as fast as you can. Are you with Derek? No, Noel, please, just get over there as fast as you can, right now!"

Still on the phone with Noel, Scott wakes Isaac and tells him to get dressed too, because Stiles is in trouble. Noel asks through the speaker what's wrong with Stiles, Scott admitting he doesn't know as we cut to Aiden and Lydia at the school.

—

After the two have a lighthearted exchange about modeling, Lydia hears something, turning her head toward the sound. She stands up and asks if Aiden hears the same voices she does, coming from the radio as we hear Stiles begging someone to come find him.

—

Stiles calls Scott back as he and Isaac go downstairs, Scott promising he only told Isaac and Noel, not his dad. Stiles says he's in some sort of basement, bigger than one in a house, probably industrial. He says he has to go because the phone is dying, and Scott asks why he's whispering.

"Because I think there's someone in here with me," he breathes out as the credits roll.

—

Kira's mom gives her a new lightbulb after hers breaks, and we see Scott and Isaac enter Stiles' room where Aiden, Lydia, and Noel are already waiting. Scott asks how they knew and when they got there, Lydia telling Scott she heard Stiles. She says her powers aren't any more confusing than Stiles' current room situation, all red lines on his boards tied to a pair of scissors on his bed.

"He uses red to symbolize unsolved cases, maybe he thinks he's linked to some of these," Noel suggests, Isaac saying "Or he's the unsolved case."

"Hold on, is he still out there? And you don't know where he is?" Lydia asks, Scott relaying the industrial basement vague location.

"We came here to get a better scent," Isaac says to back Scott up, as Noel adds "We didn't see much else we could do, especially since we aren't all that great at remembering scents to the letter."

"What else did he say?" Lydia asks, as Noel says "He says his leg is hurt, and that it's bleeding."

"And that he's freezing," Isaac adds, as Lydia asks "Freezing? What, like you froze at the Glen Capri?"

"I doubt it. That happened because I was a werewolf and under the hotel's influence, Stiles isn't a werewolf," Noel brushes the thought aside, trying to think of where Stiles could be.

"No, it's definitely not that kind of freezing, it's the coldest night of the year tonight. Temperatures are gonna drop into the twenties," Aiden says as Lydia asks what the sheriff had to say about it all.

"He kinda doesn't know yet," Scott admits, Lydia outraged that he hasn't been informed if Stiles is in so much danger.

"He made me promise not to," Scott insists, "and we can find him by scent. And if he was sleepwalking, he couldn't have gotten far, right?"

"Sleepwalking? Scott, the jeep is gone," Noel says exasperatedly, as Lydia starts to call the sheriff, noting aloud that she never promised not to tell him.

Scott insists that she waits, saying "I can get more help, I can call Allison, Noel can get Derek-"

"Everyone except for the cops, great idea!" she retorts, as Aiden reminds them all that Lydia's powers only manifest when somebody's about to die.

This seems to finally convince Scott, and at the last second, he says "You don't have to call his dad. It's only five minutes to the station."

Everyone moves to leave, but Lydia grabs Aiden's arm and says that the two of them will catch up. Noel asks her why, and she says there's something in Stiles' room.

Isaac jokes that it's evidence of total insanity she's sensing, as Scott says they can figure out what's wrong with Stiles once they figure out how to keep him from freezing to death.

Lydia tells them again to go, and the three boys leave as Aiden and Lydia hang back.

—

We see Stiles struggling wherever he is, shining his phone light down at his foot where it's caught in a bear trap. He hears rustling in the dark, calling out to whoever's there and listening to them scurry around the room.

He shines his light around, finally finding a figure in the distance. He asks who they are as they keep their back to him, dropping a piece of chalk and letting it roll toward Stiles.

When he looks back at the figure, it's gone, replaced with the Kanji for "self" on the wall. Stiles looks around desperately, but finds nothing, breathing hard fearfully as the Kanji fades away.

—

After the break we see the sheriff, visibly distraught, telling the boys that if the jeep is missing, that's what they look for first. He turns to a deputy, Parrish, beside him, telling him to put out a search for Stiles' jeep.

He tells another deputy to look for an industrial basement in town, noting that Stiles could already be hypothermic if he isn't wearing shoes and only has a t-shirt.

The sheriff tells his deputies to move and think fast, telling the three boys to follow him. They do, into a private room, where the sheriff asks them if there's anything they need to tell him that everyone else out there can't know.

"Lydia knew he was missing," Scott says, and the sheriff asks if she can help find him.

"She's working on it, she feels something but she can't place it yet," Noel informs with a nod.

"Anything else?" the sheriff asks, as Scott says that he and Noel called Derek and Allison for reinforcement.

The sheriff asks if they can find him by scent, but before he gets an answer, Parrish enters the room and tells them that they found Stiles' jeep.

—

The jeep is parked at the hospital, dead, Scott wondering aloud why Stiles would have brought it here. The sheriff says they'll find out, going inside and meeting Melissa in the front hallway.

She promises him that security is looking at every single floor, but they haven't found him yet. He asks if there's anyone looking in the basement, and she tells him to follow her as they run off toward it.

—

Up on the roof of the hospital, we see Derek, looking around. The boys meet him up there, as Derek calls out and informs them that Stiles isn't there. He then adds the word "anymore," Noel asking "Wait, not in the whole building?"

"He's gone," Derek insists, as Isaac offers to go tell the sheriff. Scott asks him to also see if he can find Allison, Isaac agreeing with a nod as he runs back into the building.

Scott and Noel walk up to Derek, as Derek asks them "Notice how strong the scent is up here?"

Noel closes his eyes and takes in a small breath, barely noticeable, slightly recoiling at the scent he picks up. "God, it's... What is that?" he asks, eyes still closed.

"Have you ever heard of chemosignals?" Derek asks, continuing "They're chemical signals that communicate emotion. Just our sweat can give off anger, fear, disgust. Take a deep breath, Scott, tell me what you feel."

Scott closes his eyes as Noel's open, taking in his breath and saying "Stress."

"Anxiety," Derek and Noel say in unison, Scott looking at the two of them as Noel looks up at Derek.

"What was he doing up here?" Scott asks worriedly, Derek admitting "I don't know. There was definitely some kind of struggle."

"With who?" Scott asks, Noel grimacing and saying "Himself." He remembers the feeling of struggling against oneself all too well from his days being host to Laura, as the scene cuts into the next.

—

At the station, McCall walks into Parrish, asking where everybody is and if they're after a lead on the "sword-wielding maniac."

Parrish says they're all actually out looking for somebody who's more top priority, McCall asking who that top priority is.

—

In Stiles' room, Aiden picks up a photo of Scott, Stiles, and Noel in their lacrosse gear, all smiling together mid-laugh. He sets it down and picks up a drawing Lydia did of a series of tree roots, as she tells him to put it back and her phone chimes.

A text from Scott reads 'Nothing at hospital. Noel and Derek headed to high school. Isaac going to find Allison. Im with Stiles' dad.'

Lydia goes back to looking around aimlessly, as Aiden plucks one of the red strings. We hear hushed whispering as Lydia asks what Aiden just did, realizing the voices only came once the string was touched.

She plucks the string herself, hearing more whispers and ducking down close to the strings. She continues to pluck, asking Aiden if he hears what she does. He insists that no one hears what she does, as she hears the words "Eichen House."

She realizes that that's where Stiles is as we go to commercial.

—

Back with Stiles, he tries to free his foot from its trap, screaming to the figure circling him who they are.

They respond in Japanese, which Stiles doesn't understand, but they elaborate that it isn't a question of who they are, it's a question of who "we" are, describing themselves and Stiles as a single entity.

They're suddenly revealed to look more akin to a thing than a human despite their voice, face a mess of bandages with a slit cut in it to show off a row of sharp teeth inside a mangled mouth.

It points out to Stiles that they stopped shivering, and Stiles knows that that's because his body is trying to conserve energy as it succumbs to hypothermia.

Stiles begs the thing to stop calling them a 'we', as it insists that he gets up and moves around to keep them from dying. Stiles insists he can't with the trap on his foot, but it points out almost smugly that it isn't real.

He realizes it's right, as the trap switches feet, and it insist that it's trying to save Stiles' life.

—

The sheriff pulls up to Eichen House, and Lydia swears that Stiles has to be there. The sheriff believes her, entering the building and requesting access to the basement areas.

McCall asks Parrish if the transcript of Stiles and Scott's phone call is exact, as Melissa shows up and offers her assistance to find Stiles.

The sheriff, Lydia, Scott, and Aiden enter Eichen House's basement and find nothing, Scott turning to Lydia and asking what happened. The sheriff raises his voice to ask her the same, as she flinches before he apologizes and she tries to listen for Stiles.

She says she doesn't understand, everyone heading back upstairs as we move past the stairwell and see the "self" Kanji from earlier on the wall.

—

McCall and Melissa have a conversation about how Stiles could still be asleep, just convinced that he's in a basement even if he isn't.

The thing with Stiles starts giving riddles, with emphasis on "when is a door not a door." It then asks him "everyone has it, but no one can lose it."

Stiles is stumped then, but it continues to repeat the riddle, waiting for an answer and yelling at Stiles when it doesn't get one.

It then begins to drag him by the chain of the bear trap, and Stiles finally wakes up screaming in Melissa's arms as she insists he's okay.

—

Isaac and Allison have a scene where Allison finds that her phone was turned off, and she has a voicemail in Japanese waiting for her.

—

Noel is working to jumpstart Stiles' jeep under Derek's patient direction, and Aiden asks if they think Stiles was just sleepwalking or if there was more to it.

Noel looks to Derek to let him speak first, and the man says simply "In this town, there's always something more."

"Rarely with Stiles, but yeah," Noel half jokes as he looks at the cables in his hands, Aiden keeping his eyes on Noel as he tells the two of them that he may know something more.

Derek and Noel look to him to continue as Derek gently instructs Noel what to do next with the jeep, Aiden cutting in "Actually, why don't you tell him, Noel? You were there."

"What are you talking about?" Noel asks, Aiden elaborating "I listened to your conversation. In the chemistry lab."

"What? Scott told you to mind your own business and give him privacy with Stiles and I," Noel says sternly, glaring daggers at Aiden as Derek asks "Noel, what was said?"

Noel looks at Derek, sighing and saying "Stiles... Stiles thinks he's the one that left the note telling Barrow to go after Kira."

"So you two think that Stiles- skinny, defenseless Stiles- is the Nogitsune? A powerful, dark spirit?"

"We're not the only ones thinking it, I'm just the only one saying it," Aiden says with a pointed look at Noel, who bristles and glares as he goes back to fussing with the cars.

"This thing wants to possess somebody and it chooses Stiles? Why not take someone bigger, stronger, someone with a little more... Power," Derek trails off at the end, looking over at Noel just as the boy touches his two cables together and creates a spark on accident.

—

In the hospital, the sheriff informs everyone that Stiles is asleep, doing just fine, and that he doesn't remember much. He thanks McCall, who finally reveals that Stiles was in Malia's old coyote den (the smell that made Stiles' eyes water was the animal repellent that was sprayed in the den to ward off other animals).

Melissa tells Scott and Lydia that they have school in less than six hours, urging them to go home and get some sleep.

"And hey, I last saw Noel in the parking lot, please go grab him and make sure he gets some good sleep too. I worry about him," she adds, Lydia nodding with an uneasy smile.

The two teens begin walking away, as Lydia laments how she was so sure where Stiles was only to be proven completely wrong.

Scott points out that he wasn't much help either, as Lydia begins to hear something. Scott asks if she did, but she lies, claiming it was nothing.

—

The next day at school, Scott texts Deaton asking if he's found anything, but Deaton says there's nothing yet. Scott leaves the locker room and ignores Kira when she calls out to him, leaving her confused.

"He's a little preoccupied," Derek says just offscreen, as Kira turns to face him. "But I can help you."

"You're... Noel's boyfriend," Kira asks, as if confirming, Derek chuckling and nodding. "Yes, I am. But my name is Derek."

"Why would you want to help me, Derek?" she asks, as he admits "Because I want you to tell me everything that happened at the power station with William Barrow. Actually... I want you to show me."

—

The sheriff checks in on Stiles, and Melissa and he have a vague conversation that ends in the sheriff requesting they do some testing on Stiles.

—

Then, we see Derek and Kira, at the power station. Kira tells him where everything happened, and while they're there, Derek finds Stiles' baseball bat stuck magnetically to a wall.

He sees how strong the magnetic pull is, turning back to Kira and asking her to tell him everything she knows about foxfire before gesturing to a high voltage sign.

—

At school, Allison and Isaac are having Mr. Yukimura translate the voicemail on Allison's phone, and he tells then it's an old WWII Japanese internment camp instructional announcement. But he tells them it isn't real, because the internment camp cited in the voicemail ("Oak Creek") doesn't exist.

—

A locker slams and clearly causes Lydia distress, as Scott and Noel stand on either side of her. She admits that she's hypersensitive to loud sounds today, as Noel asks "Want me to say something to that dude?"

Before she can answer, another locker abruptly closes, as Scott turns toward the sound and tries to change the subject.

"They're doing tests on Stiles all afternoon," he tells the two others, adding "I was gonna head over around six to visit. Do you guys wanna come with me?"

"I should probably just go home," Lydia says in monotone as Noel gives her a look of concern, another locker slamming as she jolts.

"Lydia, are you sure you're okay?" he asks and puts a gentle hand on her shoulder, but she shrugs him off and says "I'm fine. I'll text you both later."

She then walks away, Noel and Scott giving each other worried glances.

Lydia has a short sequence of herself jumping at sudden noises, and then we go to the hospital, where Stiles is preparing for his tests.

—

Save for a brief "Noel's gonna be here later, he just thought you might want some extra privacy right now," from Scott at the very top of his and Stiles' conversation, the scene of Stiles' MRI prep is unchanged.

—

Kira and Derek pull into the hospital, but Kira is wary of their plan. She points out that essentially, Derek's going to tell Scott that her foxfire was used to jumpstart the Nogitsune inside Stiles, and Derek agrees that she should probably stay outside.

As he turns to walk in, Noel pulls in in front of him, stopping him in his tracks and asking "Derek? What are you doing here?"

Derek looks back at Kira, who shrugs helplessly, as he says "Long story. Come on up with me, I'll tell you on the way."

—

Stiles' MRI scene is unchanged, as is the scene where Lydia hears the clanging of the machine and tries to drown it out by playing loud music in her car.

—

Scott, Derek, and Noel sit in the waiting room of the hospital, Scott initiating conversation with "You know that stuff you were telling me about chemosignals yesterday? It reminded me of the time you were teaching me to use anger to control the shift."

"I think you ended up teaching me more about that," Derek says and reaches over to Noel with a soft smile, wordlessly taking his hand as Noel smiles and squeezes back gently.

"You're teaching me again," Scott says with a smile at the two of them, as Derek says "Think of it more like... Sharing a few trade secrets."

Scott nods as Derek looks between him and Noel once, taking in a breath and saying "You know I took Cora back to South America, right? It's where she spent most of her time after the fire. But that's not the only reason I left."

He takes a brief pause, looking at Noel, because this is the first time he's hearing this too. He takes a small breath, admitting "I needed to talk to my mother."

"Your dead mother," Scott asks, like he didn't hear Derek correctly, as Noel gives him a look and Derek continues.

"She told me something that changed my perspective on a lot of things. She said my family didn't just live in Beacon Hills, they protected it. This town needs someone to protect it, someone like you."

"And it needs someone like you to teach its new protector a few trade secrets," Noel points out and gives Derek's hand a squeeze, as Scott has a realization.

He stands up, saying "He was trying to protect us... Stiles was protecting us." As if they realize it at the same time, Derek and Noel say in unison "from himself."

Their hands clench together tighter, and suddenly we're back on the roof of the hospital.

—

"What are we looking for," Derek asks, as Scott admits he's not sure.

"Maybe a sign that points to what he was struggling to stop," Noel suggests, looking all around on the roof as the three all search in different places. Scott reaches up and swipes a bag full of tools onto the ground, as the three all look up and see a sparking live wire.

In her car, Lydia gives a silent scream, and we cut to commercial.

—

After reviewing the results of Stiles' MRI, in which we learn he's developing frontotemporal dementia like his mother, Stiles slips into another dreamlike state where the thing asks him if he's found out its riddle yet.

The thing promises that if Stiles figures it out, it'll let his friends and family go. The thing becomes seemingly agitated, starting to unwrap the bandages that make up its face, screaming at Stiles to give it the answer to the riddle.

Once the bandages are all off, Stiles finally figures out that the answer to the riddle is a shadow, and Void Stiles (who we will simply call Void for ease of distinction) is revealed.

Void wakes up, in control of Stiles' body, and looks around the MRI scanner. He suddenly disappears in a blackout to the sheriff's outrage as the single spark on the roof bursts into a shower that sends Derek, Noel, and Scott scurrying backwards.

Their faces are illuminated white by the shower, Derek's arm in front of Noel keeping him back and away as the sparks fly.

A wire begins to snap around with sparks on the end, as Void ties his shoelaces and watches people rushing around the hospital around him.

In the elevator stands Noshiko Yukimura, making eye contact with Void as he approaches her with a smirk.

"You know me," she notes with almost a smile, continuing "Then you remember that I won't be deterred by your choice of host. Even if it's an innocent boy."

"Are you threatening us?" Void asks, as Oni pop up on either side of Noshiko, and she confirms "Now I'm threatening you."

"We're not really afraid of your little fireflies," Void muses, turning to walk away.

"If the Oni can't defeat you, I know someone who will," Noshiko swears, as that gets Void's attention.

—

Kira watches the live wire snapping and sparking on the roof, as it falls down in her direction and whips toward her.

—

With that, the episode abruptly ends.