|“|| "You don't understand, do you? It's a riddle. Do you know any riddles, Stiles?"|
"What gets bigger the more you take away?"
"What gets wetter the more it dries?"
"When is a door not a door?"
"...When it's ajar."
"Everyone has it, but no one can lose it. What is it?"
"Everyone has it, but no one can lose it. What is it, Stiles?"
"I don't-I don't know!"
Stiles makes a panicked late-night phone call to Scott after he finds himself in a strange location with his leg in a steel trap. Lydia leads them to the mental health center where Barrow was committed, only to find that Stiles is not there. Scott's mother and father find Stiles, who had been sleepwalking. Derek and Kira find Stiles's baseball bat at the power station, and Derek deduces that Kira was indirectly responsible for the Nogitsune taking over Stiles's body. Stiles has an MRI scan to test for frontotemporal dementia, the same illness that caused his mother's death. The power then goes out, due to the Nogitsune having damaged the wiring on the roof the previous night. The Nogitsune, now in complete control of Stiles's body, confronts the remaining Oni, who are revealed to be led by Kira's mother.
- Tyler Posey as Scott McCall
- Crystal Reed as Allison Argent
- Dylan O'Brien as Stiles Stilinski
- Tyler Hoechlin as Derek Hale
- Holland Roden as Lydia Martin
- Melissa Ponzio as Melissa McCall
- Linden Ashby as Sheriff Stilinski
- Daniel Sharman as Isaac Lahey
- Arden Cho as Kira Yukimura
- Max Carver as Aiden
- Matthew Del Negro as Rafael McCall
- Tamlyn Tomita as Noshiko Yukimura
- Tom T. Choi as Ken Yukimura
- Aaron Hendry as Nogitsune
- Brandon Boyce as Dr. Vandenburg
- Ryan Kelley as Deputy Jordan Parrish
- The title refers to the various riddles that the Nogitsune asks Stiles when he was sleepwalking and ended up near-hypothermia in the coyote den. These riddles include:
- What gets bigger the more you take away? (A hole)
- What gets wetter the more it dries? (A towel)
- When is a door not a door? (When it's ajar)
- Everyone has it, but no one can lose it-- what is it? (A shadow)
- McCall House
- Scott's Bedroom
- Living Room
- Beacon Hills High School
- Art Room
- Locker Room
- Yukimura House
- Kira's Bedroom
- Stilinski House
- Stiles' Bedroom
- Beacon County Sheriff's Department
- Sheriff's Office
- Eichen House
- Beacon Hills Memorial Hospital
- Emergency Room Lobby
- Parking Lot
- MRI room
- Beacon Hills Preserve
- Coyote Den
- Electric Substation
- Argent Apartment
- Allison's Bedroom
- "Let Me Be" by Harleighblu
- Lydia is sketching in the art room at school after-hours while Aiden models for her
- "A Million Drums" by Claire
- The light bulb in Kira's lamp goes out while she's studying, and when she goes to unscrew it, electricity flickers from her fingers into the bulb, making it glow so brightly it explodes
- "Gallows Strung" by Snow Ghosts
- Kira calls out to Scott at school, but he's too distracted to notice. Derek sees this and tells her that Scott is preoccupied before offering to help her himself
- Slippin Around" by Zhala
- Lydia is sitting alone in her car in the hospital parking lot, where she's overwhelmed by a Banshee premonition of Stiles getting his MRI, causing her to flinch at the loud clanging sounds she hears until she finally screams to get some relief
- "The Call" by Ruu Campbell
- Dr. Vandenburg tells Sheriff Stilinski and Melissa that Stiles' MRI shows signs of frontotemporal dementia