"Come on, Elle, we've all asked him, and he won't say. He wants us to figure it out." Derek says as Jessica walks back over to her desk after getting coffee.

"Oh, God, is this about the Foothpath Killer again?" Jessica asks, groaning in annoyance. "He's not gonna tell anyone."

"Okay. I'm up for a challenge." Elle says, leaning against her desk.

"Good, because these go to you." JJ puts a stack of files on Elle's desk. "Special Agent Jennifer Jareau. JJ if you like." She holds her hand out and Elle shakes it.

"Elle." She introduces herself.

"Greenaway. Highest number of solved cases in Seattle 3 years running, specialty in sex offender cases." JJ says.

"Not bad."

"Well, I'm the unit liaison. My specialty is untangling bureaucratic knots. You'll probably be talking to me a lot. My door's always open, mostly because I'm never in my office." JJ says while making her way to Hotch's office. "So just call me on my cell, okay? We'll talk."

"Did you watch it?" JJ asks Hotch as he walks out of his office.

"Yeah. Think everybody should see it." He says. "BAU team, can you meet me in the conference room, please? I need to show you something." He states and they all follow him to the conference room.

"This is from the Phoenix office, Bradshaw College in Tempe, 6 fires in 7 months." Hotch says.

"Who recorded it?" Gideon asks.

"A student with a digital camcorder. He was watching a fire in the building across from their dorm. The other person you'll see is his roommate, 20 year old Matthew Rowland." JJ says before starting the video.

"This is crazy." The student recording says, zooming in on the fire across the street. "Hey, Matt, get over here. You gotta see this. The building's on fire."

"Bro, you getting this?" A guy steps into the frame.

"Is that the kid?" Gideon asks.

"Yeah, that's him." Hotch says.

"Relax, man. There's always fires during rush week."

"Yeah, but that's pretty big. What building is that?"

"Dude, over here. Check this out."

"What is it?"

"I don't know, but it's coming underneath the door."

"Is there someone in the hallway?"

"Hey, someone's trying to get in."

"Hey, man, you should get in there."

"Oh, my God! It smells like gas."

Fire flames from underneath the door and sets one of the guys on fire while both yell out and scream. The one recording drops the camera and starts to try to put his roommate out.

+++

"There are 2 common stressors for a serial arsonist." Spencer says.

"Loss of job, loss of love." Elle says.

"When was the first fire set?" Derek asks.

"March. Uh, the next one was in May." Hotch informs, flipping through the file. "And the third one wasn't until September. Then two weeks later there were three in one night."

"He's speeding up. Fires are closer together." Gideon says.

"Hey, Reid, you got a statistic on arsonists?" Derek asks.

"82% are white miles between 17 and 27." Spencer states. "Female arsonists are far less likely, their motive typically being revenge."

"Sounds like our boy's a student." Derek says.

"Don't be so sure." Gideon argues. "You rely too much on precedent, you never allow for the unexpected. If he went from setting one fire to three in two weeks' time..."

"Rapid escalation." Hotch says.

"He's gone from the power to damage the building to something far more satisfying. The power over life and death." Gideon says. "Who we talking to first?"

"Dean of students, Ellen Turner." Hotch states.

+++

They get to the college and get out of the cars.

"No badges. I don't want to satisfy the unsub's need for attention by letting him know we got the FBI here. Try not to look official." Gideon says. He looks back at them, glancing over their outfits. "Try to look less official."

~ ~ ~

"Obviously, I'd rather be meeting you under different circumstances. This is fire inspector Zhang." The dean informs.

"This morning, the chemistry department reported several bottles of highly flammable chemicals missing." Zhang says.

"I'm prepared to evacuate this campus." Ellen says as Gideon opens the door. "Thank you." She tells him, walking in, the others following.

"That brings on its own problems." Hotch says.

"You might evacuate the arsonist as well." Gideon says.

"Well, then the case go unsolved, the campus is reopened, but the fires start up again." Jessica says.

"Hotch, Gideon, hold on a second." Derek stops them. "You said the chemicals were missing today."

"Uh-huh." Zhang nods.

"It says here that one of the previous fires was set with diesel fuel that disappeared from the grounds keeping facility. How long after it disappeared was the fire set?" Derek asks.

"One day." Ellen says.

Gideon and Hotch walk off.

+++

"He turned the water off just before the fire." Zhang says. "The last three were set with these." He says, opening a box. "Two devices, simultaneous ignition."

"There was no device used on Matthew Rowland." Gideon says. "Unsub set that one manually?"

"He wanted to be there to enjoy the kid's death." Derek says.

"Not necessarily." Hotch argues.

"Well, if the target was Matthew Rowland, then why set the other two fires?" Elle asks.

"The motives for arson are relatively simple. There's vandalism, crime concealment, political statement... profit." Spencer lists.

"And revenge." Hotch adds.

"We interviewed Matthew Rowland's roommate. He said Matthew was very well-liked. No reason for revenge." Zhang says.

"What about vandalism?" Ellen asks.

"No, the fires are too sophisticated." Elle says.

"Yeah, and if he's trying to make a political statement, he's not being too clear about it." Jessica says.

"There's an underlying strategy in this case." Gideon says. "Matthew, firefighters, injured victims. To the unsub, they're not people. They're..."

"They're objects." Hotch says.

"More like, uh..."

"Chess pieces." Spencer says.

"Exactly." Gideon says.

+++

"The timer sets the road flare, which then lights the chemical mixture inside the canister. Simple." Elle says.

"Yet sophisticated in its simplicity. I mean, there's a meticulous construction to it." Spencer says.

"Chemical accelerant could mean chemistry student." Elle suggests.

"Could also mean chemistry professor." Spencer says.

"Mmm, I say student. You need self-confidence to lecture in front of a classroom full of 30 college kids." Elle says. "Arsonists are socially incompetent. This guy, he doesn't go on dates. He doesn't go to parties. He doesn't feel comfortable in front of groups."

Spencer looks over at her. Jessica winces.

"And, of course, he's a total psychopath." Elle adds.

"Of course." Spencer lets out a quiet laugh. Jessica gives Elle an amused look.

+++

There was another fire earlier, a professor dying. Elle took pictures of people's reactions, the team inspecting them.

"We've been at this all night, and we've got nothin'." Derek says. "Look at these expressions. We've got fear. A touch of horror, even a little bit of panic. Where's the guy gettin' off?"

"When asked about his motives, Peter Dinsdale said, "I am devoted to fire. Fire is my master."" Spencer says.

"Okay, so who was our boy's master?" Derek asks. "10,000 plus students..." He flicks his lighter on. "And one has a serious fascination with fire." He shuts the lighter.

"Fire starting is one third of the homicidal triad... an early predictor of adult dissociative criminal behavior. If we looked in his childhood, we'd probably find all three. Fire starting, bedwetting, and cruelty to animals." Jessica says.

"Absent or abusive father, trouble with the opposite sex, chronic low self-esteem -- M.O. would be dynamic." Gideon says. "Evolvings, fire setting escalates, they thrive on panic, fear. It's just standard profile of a serial arsonist."

"Based on hundreds of interviews." Spencer says.

"Based on precedent." Derek says.

"Everything the unsub should be, according to research." Jessica says.

"We're off the mark." Hotch says.

"Because of the two missing elements." Gideon says.

"Sex and power -- the two motives that drive a serial arsonist." Derek says.

"And without 'em, we do not have a profile." Gideon says.

+++

Jessica, Hotch, and Spencer are in the chemistry lab, four students in there, claiming they know how the unsub is starting the fires.

Spencer is fiddling with some vials while Jessica messes around with a microscope.

"Reid, Taylor." Hotch walks over. "Since you're both more their age, why don't you do the talking?" He suggests before walking away, going over to where Zhang is.

"Not it." Jessica says the moment Spencer looks at her.

"Wha-- but--" Spencer frowns.

"I taught you the rules of "not it," abide by them." Jessica orders. "Get to talking, Dr. Reid." She says, trying to hide her smile at the annoyance on his face.

"Hi-- hi, guys." He stutters. "Uh, my name's, uh, Dr. Spencer Reid." He picks up a light bulb and messes with it. "I'm a, uh, agent at the-the-- the BAU, the Behavioral Analysis Unit of the FBI which, um, it used to be called the BSU, the Behavioral Science Unit, but not anymore." He rants, walking closer. "They changed it to the BAU. Um, it's part of the N.C.A.V.C. -- the National Center for the Analysis of Violent Crime -- which is also part of this thing called the CIRG -- the Critical Incident Response Group, and--"

"What he's trying to say is we'd love to know how you can help us." Hotch cuts in.

"May I, please?" Jeremy stands up, holding his hand out for the light bulb in Spencer's hand. He gives Jeremy the bulb. "Thank you." He holds it up. "See this? Drill a hole in the side, fill it with gasoline or whatever's good and flammable. Turn the light on. Boom. That is what went down, didn't it?"

"Th stuff's all over the net." They turn to one of the girls. "Wanna know how to make a molotov cocktail that sets itself on fire? Potassium, sulfur... and normal sugar. Sugar. Sugar. Which is--"

"Not exactly plutonium." Jeremy says. "You could get this stuff anywhere."

"Sugar from the supermarket." The first girl says.

"But you don't need to be a chem major to know that." Hotch says.

"Do you think it's a chem student?" Zhang asks.

"You wanna know what I think? I think... it would be a good time to take the semester off." Jeremy says. He gives the light bulb back to Spencer.

~ ~ ~

Hotch hits the floor button he wants on the elevator and Jeremy uses a key, twisting it.

"Hold on. You need a key to get it movin' after 10:00 PM." Jeremy informs.

"Well, if it's a such a good time to take the semester off, what are you still doing here?" Jessica asks.

"I can't leave. We've all got projects. You know how to solve the 3 body problem?" Jeremy asks. Jessica glances over at Spencer when he nods. "Computing the mutual gravitational interaction between the earth, sun, and moon?"

+++

"Karen. I do this for Karen." The recording says.

"Play it again." Gideon says.

"The call came from the office right next to the Wallace's five minutes before the fire was started." Derek says.

"Play it again." Gideon orders and Derek does so.

"Karen. I do this for Karen." The recording says.

"Again, louder."

Derek turns the volume up, turning the speaker to Gideon, and presses play again.

"Karen. I do this for Karen."

"What is it?" Hotch asks.

"I'm not sure. Somethin' about it." Gideon says.

"Is this tape clean?" Hotch asks.

+++

Jessica and Spencer are sitting on the ground under a tree. Gideon is walking around.

"What if the unsub is one of the students leaving?" Spencer suggests.

"No, he's not done yet. He's not goin' anywhere. Keep thinkin'." Gideon says.

"You mean, out-- outside the box? That's what Morgan's always telling me. He says that's why I can never beat you at chess." Spencer says.

"Well, he's probably right." Gideon says.

"But, I mean, in this situation, what exactly is the box?" Spencer asks.

"The standard profile of a serial arsonist. If everything you know goes in the box, what's left?" Gideon asks.

"What you don't know. The unknown." Spencer says.

"Sometimes you have to get creative. Even if you think it's utterly unlikely, you have to think of things nobody else thought of." Gideon says.

"Like a stutter." Spencer says.

"Yeah, exactly." Gideon nods.

+++

"Hey, Reid... Garcia says it's not "Karen." It's actually somethin' more like--" Morgan is cut off as Gideon rushes in.

"Charon." Gideon states.

"Charon?" Spencer asks.

""Charon. I do it because of Charon."" Gideon quotes.

"That's Hebrew." Spencer realizes.

"It's God's word in anger." Gideon says.

"Yeah." Spencer nods.

"The motive is now religious?" Elle asks, walking in with some food.

"Well, you know, in a lot of religions, God is related to fire." Spencer says.

"Well, Brahman is fire in Hinduism, and the Jews see God as a pillar of fire, and Christians worship God as a consuming fire." Hotch says.

"Okay, so we're lookin' for a theology major." Derek says. Elle tosses Spencer a container of food and he looks at it.

"I don't want this." He says, putting it down.

"What-- what's the most sinful place on campus?" Elle asks.

"Come on, Elle. When I was in college, that was everywhere." Derek says.

"Yeah, agreed." Jessica says, pointing to Derek.

"A fraternity?" Hotch asks.

"A campus bar?" Elle suggests.

"No, cause that's not consistent with the previous targets." Hotch argues.

"What about the idea of baptism by fire? Aren't we all supposed to be tested through fire in Revelations?" Derek asks.

"Look, it's good, it's good, but let's please do not jump to conclusions. Religion might be a part of it, but it's not necessarily the prime compulsion." Gideon says.

"Gideon, rush to conclusions, jump to conclusions. Who cares?" Derek remarks.

"We are running out of time." Elle says.

"Compulsion." Spencer mumbles.

+++

Jessica, Hotch, and Gideon are going over their research, when Spencer walks in.

"I know why the profiles never fit." Spencer says. "You were right to tell Morgan not to rely on precedent. The fires thus far have been completely task oriented."

"So once they're set, the unsub is done?" Hotch asks.

"Exactly. The unsub isn't a classical serial arsonist. He's someone who uses fire because of a completely different disorder." Spencer says.

"Which is?" Jessica asks.

"An extreme manifestation of OCD, obsessive compulsive disorder." Spencer states. "He does everything in 3s, and if I'm right, he'll have to kill again."

~ ~ ~

"There's a form of OCD called scrupulosity." Spencer says.

"Religious obsession and compulsion." Hotch says.

"An obsessive fear of committing sin, which creates so much anxiety that he's compelled to do something to ease that anxiety." Spencer says.

"Like setting fires." Jessica says and Spencer nods.

"Where's the behavioral evidence?" Gideon asks.

"Right here." Spencer turns to the video. "All right. Remember the night of the 3 fires? We saw the doorknob turning against the lock." He shows a video of the doorknob, it zoomed in. "But he's not trying to get in. He's compelled to turn the doorknob 3 times."

"Well, what about the fires?" Gideon asks. "The first ones were single fires. If the unsub was OCD, shouldn't they have all been in 3s?"

"They were in 3s. A trinity of 3s." Spencer states. "The first fire occurred on March 3rd."

"3:00 PM. Third day, third month." Gideon says.

"It's that convergence of 3s that causes the overwhelming anxiety." Spencer says. "Obsessive compulsives ease the anxiety by performing the compulsion."

"What about the other fires? Professor Wallace?" Hotch asks.

"Office number 3." Spencer states. "I checked for more patterns of 3s. His class was on Tuesdays."

"Third day of the week." Hotch says.

"Matthew Rowland was in that class. It was his third class of the day. If we looked into each of the fires, we'd find a lot of patterns having to do with 3s because our minds are incredibly adept at seeking out patterns." Spencer says. "But to the unsub, once that pattern hits, bam--" He snaps, "he sets a fire."

"But if the target was always people, why did no one die in the first few fires?" Gideon asks.

"They were failures. Up until Matthew Rowland." Spencer says.

"What is it?" Gideon asks, noticing Hotch's look.

"I think I know who it might be." Hotch says. "And it's not a he. It's a she."

~ ~ ~

"When I was talking to her and her classmates, I noticed something -- a ring on her finger. And she kept turning it." Hotch says.

"At intervals?" Spencer asks.

"Of 3." Hotch states. "And she counted off the ingredients of a light bulb bomb."

"And the word "sugar."" Spencer says.

"Yeah. And She kept repeating it." Hotch says. "Once she started, she couldn't stop."

"it's palilia -- the involuntary repetition of words." Jessica states.

"Howard Hughes had it when his OCD worsened." Spencer says.

"Clara and her classmates were working on a project about gravitational pull." Hotch says.

"The 3 body problem." Gideon says.

+++

"Moloch was the demon sun god of the Canaanites. In order to keep from incurring his wrath, the people would sacrifice their children to him by burning them alive." Spencer informs.

"16 year old survives inferno." Hotch says, grabbing the piece of paper. "The mother Ellen Hayes called it a miracle. "My daughter was tested by God. He tested my child and she came through blessed."" He reads. "Look at the house number." He gives the paper to Gideon.

"333." Gideon says.

+++

"Security's checking the science building." Ellen states.

"Well, where else would she be?" Gideon asks.

"We need to find the next pattern of 3s." Spencer says.

~ ~ ~

"Morgan, seal the building, get out of there, and walk away." Hotch orders.

"We need to send our people into every building and have them start pulling fire alarms. Please, go." Gideon orders the cops. "Mead, a map of the campus. We need to find anything and everything having to do with the number 3." The cops and Ellen rush out. "Where's the blueprint?"

~ ~ ~

"Jason, wait. Wait, wait, wait." Hotch stops him. "Clara Hayes is very likely a good person. Someone who never wanted to do anyone any harm, like any other rational person. But there's nothing rational about obsessive compulsive disorder."

"Research suggests OCD involves problems in communication between the frontal part of the brain and the orbital cortex." Spencer says. "Plus deeper structures. The basal ganglia."

"You can't reason with her because you can't reason with a physiological problem." Hotch says. "She's not setting these fires because she wants to, but because she has to."

"What are you trying to say?" Gideon asks.

"Don't try to convince her to stop because you won't be able to." Hotch states and Gideon nods.

~ ~ ~

"We're still looking." Spencer tells Gideon, having the phone on speaker.

"Focus on the girl." Gideon says.

"She's failing out. This was gonna be her last semester." Spencer informs.

"That's the stressor. What else?" Gideon