"Ghouli" is the fifth episode of the eleventh season of The X-Files. It is written and directed by James Wong.
When a pair of teenage girls attack one another, each believing the other to be a monster, Mulder and Scully find that their investigation could possibly lead back to their long-lost son, William.
Two teenage girls, Sarah Turner (Madeleine Arthur) and Brianna Stapleton (Sarah Jeffery), enter a rusted out and abandoned ship, named “Chimera.” Each enters on their own, scoping out the docked vessel in the middle of the night. They hear each other’s steps, going around different levels of the ship. Both girls accuse each other of being "Ghouli." The brunette girl grows impatient and runs across the rotten wood deck that collapses under her. She lands inside the bridge, where the terrified blonde girl screams, wielding her knife at her. Each sees the other as the Ghouli. They end up stabbing each other.
Dana Scully (Gillian Anderson) opens her eyes in the dark, laying on her side on a bed. Meanwhile, a dark figure looms behind her. She senses the presence and struggles to get out of her bed. She explores the mysterious house and ends up in a endless pattern of the same room. It all turns out to be a dream. Fox Mulder (David Duchovny) theorizes that the experience as a type of sleep paralysis. She tries to remember when she spots a picture on Mulder’s desk of the Chimera ship. She goes back to her memories of her sleep paralysis, where she grabs a snow globe with a model of the boat in it.
Mulder and Scully get to the dock, meeting with Detective Costa (Louis Ferreira). At the scene of the crime, Scully notices a bloody handprint left by one of the girls on the glass of the bridge and questions who made the call. Costa informs them that it was an anonymous 9-1-1 call from a panicked male. Later, Scully’s attention is drawn to a man that observes them intently from one of the portable walkways. Costa informs them that the victims asked if they found Ghouli. When Scully turns to check if the mystery guy is there, he’s gone.
Mulder and Scully are sitting at a coffee shop and checking the internet. They come across Ghouli.net. Both agents investigate the two teenagers about the slashing. Both of them go on about the experience and their boyfriend, Jackson Van De Kamp. Scully recognizes the last name as her missing son's adoptive parents. The agents arrive at the Van De Kamp household, the same house Scully saw in her dream. Two gunshots are heard and they dash to the entrance of the house. A man and a women's bodies are lying on the floor. A third shot is heard from the upstairs. Scully goes up and finds the bleeding corpse of Jackson Van De Kamp. Medicals are called to investigate the household. Scully and Mulder find Jackson's room and a book “The Pickup Artist. Memoirs of a Wolf in Sheep’s Clothing” by Peter Wong. Mulder turns to the window, to see the flurry of cops and emergency personnel. Scully spots a snow globe with a windmill trapped in a keepsake alluding to “The Wizard of Oz” with the phrase “We’re not in Kansas anymore.”
Scully enters the small-sized morgue where they hold Jackson Van De Kamp’s body. She carefully unveils the boy’s face, matted with dried blood. She sits by his side and begins talking to him, not knowing if he could be her son. Mulder ushers her out of the room with him. As they leave the room and the door clicks closed, the zipper opens slowly. Jackson sits up and escapes the room. Scully is lying on a couch and has another experience with sleep paralysis, with flashes to the bridge, the UFO hovering above, and the bloodied alien hand. Scully is awaken by Dr. Harris, who asks about where the body has gone. The agents now realize that Jackson's body has disappeared. Scully runs into the mystery man that she spotted at the docks, Peter Wong. Wong questions Scully about her windmill and tells her to not give up on the bigger picture.
Mulder meets with Skinner at the Chimera, telling him to drop the investigation. Mulder confirms that Jackson's DNA matches Scully's. Mulder leaves, and Skinner stays behind, at a loss. Scully and Mulder assume that William is at the hospital that the two girls are being cared to at. At the hospital, Jackson explains to Brianna that he’s been hiding because there are people after him. He reveals that Ghouli doesn't exist and it's just something he "made up". Mulder and Scully arrive at the hospital and meet up with Costa who tells them that Jackson is alive. It turns out that Sarah sent Costa a text with a picture of Jackson and Brianna kissing. Jackson gets out of the room in a rush but gets intercepted by one of the DOD. The DOD chases him into a room with equipment. He resorts to projecting himself and makes one of the DOD guys think that the other is a monster. He shoots and inadvertently kills his partner. Jackson hides under a desk, while Mulder and Scully find two other DOD members on the ground. Jackson escapes by projecting himself as a scared nurse.
The next day, Scully spots a rural gas station that has a windmill just outside. Mulder goes to use the restroom and Scully meets with Peter Wong. Both of them engage in a conversation with Wong mentioning that he wishes he could know her better. Wong gets in his car and drives away. Mulder comes out and remembers Wong, the pick-up artist from the novel. The agents ask to see the recording tapes. In the recording, Scully is having a conversation with William. She smiles as Mulder holds her while they see their son, alive.
- James Wong on writing Scully thinking her son was dead: "Writing it was… I don’t want to say it was simple, but it was something I was thinking about for a long time as a parent and as a parent of an adopted child. I had all of these things I was thinking about anyway. [Laughs] So that came quickly. I prepared for Gillian’s scene by basically getting a bunch of cameras together. We had more cameras than we normally have in the scene and just stacked them up. Gillian is a very instinctual actor, and she knows what she’s going to do. I just wanted—without having to do it over and over again—to get all the angles at the same time, basically. I talked to Gillian, and she was like, “Let’s do the meat of the scene—which is all the emotional stuff—right away, and we’ll do it first. And the prelude to that moment, we’ll shoot after.” So our plan was to stack 'up' the cameras and Gillian came on and she was ready. We did it in I think three takes. She was super prepared, she knew what she wanted to do, and did it
- Mixing Monster and Mythology together: "we wanted to have a touchstone to the mythology of it all. [Executive producers] Chris [Carter], Glen [Morgan], Darin [Morgan] and I all talked about the idea of William. But I also loved the monster episodes. [Laughs] So it was how can we meld those two ideas that I love 'into' something that is connected to William. And then you go, 'wait' a second, William has special powers. So all of those ideas thread into each other and became this episode. I love hinting at one thing and the reality is different." 
- This is the first mythology episode of the revival not to carry the title "My Struggle".
- The Ghouli character, seems to be pulled from the Internet phenomena known as "Creepypasta", where every user offers a slight variation of an "Urban legend".
- A case of "Creepypasta" coming to life would be that of the "Slender Man" in the United States, which may or may not be the inspiration for this installment of the X-files. With respect to "Slender Man", two Wisconsin girls try to murder their fellow classmate, in order to impress the fictional character, so that they might reside in his home in the woods.
- This is the first time that Mulder used his FBI badge only, and not his photograph ID.
- David Duchovny as Special Agent Fox Mulder
- Gillian Anderson as Special Agent Dana Scully
- Mitch Pileggi as Assistant Director Walter Skinner
- William B. Davis as Cigarette Smoking Man
- Miles Robbins as Jackson Van De Kamp/William Mulder
- Sarah Jeffery as Brianna Stapleton
- Madeleine Arthur as Sarah Arthur
- Louis Ferreira as Detective Costa
- Cameron Forbes as Dr. Harris
- Sunita Prasad as Dr. Aliyeh Scholz
- Keith Arbuthnot as Ghouli
- Devon Alexander as Barista
- Troy Anthony Young as Mr. Van De Kamp
- Robyn Bradley as Mrs. Van De Kamp
- Eddie Flake as D.O.D Operative
- Mackenzie Murdock as Gas Attendant