Summary: Out of all the men in JJ's life, Spencer Reid scared him the most.

Hey, so this is my first fanfic for criminal minds. I always wondered what the team's reaction to Will would be, and thus this one-shot was born :)

It was the annual Christmas party for the BAU. All was as it should be; Garcia and Morgan grinding on the dance floor, Emily drunkenly flirting with men half her age, and Spencer Reid sitting in a corner with his Pepsi ignoring all offers to dance. The only difference this year was that JJ's getting-serious boyfriend Will had tagged along for the first time. He had moved up from New Orleans in October just to be close to her, and if you listened to Garcia's gossip for more than a few minutes, you would find that the couple was thinking about moving in together.

Now, as tradition demanded, he had received subtle threats from most of the men at this party. Rossi had simply told him that if he messed up, he was going to be shot. Will was pretty sure that the next time he saw Rossi reach for his gun, he was going to dive for cover. Preferably behind JJ. Morgan had been more joking about it, saying that he should just agree with everything JJ said and that would guarantee his next birthday. That had made him relax slightly, giving him a small feeling of acceptance as Morgan continued to tease and laugh with him. That all went away as Aaron Hotchner set his glare on high and told him that it would be in his best interest not to hurt JJ in any way. That had sent him back over to cower behind JJ, who was playing darts with a very drunk Emily Prentiss.

If there had been one person that Will thought wouldn't try to threaten him bodily harm, it would have been Spencer Reid. The kid wasn't exactly Mr. Intimidation, even if JJ was like an older sister to him. Besides, Will had already met him on several occasions and Spencer seemed to like him pretty well.

Later on in the evening, Will was sitting with JJ and Spencer at one of the small round tables toward the back of the bar, eating ice cream cones.

"…and the first true edible conical shaped cone for serving ice cream was created at the St. Louis World's Fair by Ernest Hamwi in 1904. His waffle booth was next to an ice cream vendor who ran short of dishes. Hamwi rolled a waffle-" Reid had been going on for about ten minutes before he was interrupted by Morgan, who received grateful glances from the couple sitting across from the young genius.

"Would the beautiful lady care to join me in some frolicking on the dance floor to this lovely Christmas selection?" Morgan slurred as Santa Claus is Coming to Town started blaring out the speakers.

"Are you drunk?" JJ asked, laughing as Derek struggled to stand upright.

"I only had one." He whined, holding up two fingers. "C'mon, you know you want to dance with me, I love you!" JJ laughed again, shaking her head at his wild behavior before standing up.

"Just one song mister." She gave Will a kiss on the cheek and then disappeared into the crowd, Leaving him alone. With Spencer Reid.

"So, Will." Will turned his eyebrows knitting together as he tried to identify what had changed in the young man's voice. It still seemed cheerful and happy, but there was a darker undertone that Will had never heard from Reid before.

"Do you know who Dr. Joseph-Ignace Guillotine was?" Will didn't respond, simply waiting for the young genius to continue on with whatever rant his was preparing to throw out. When Reid didn't say anything else, Will cleared his throat.

"Um, no, but he does sound kind of familiar." It was awkward, but Will was pretty sure it was the first thought he had gotten in edge-wise during a conversation with Dr. Reid.

Spencer hummed quietly before giving Will an intense stare that made him shift in his seat uncomfortably. He didn't think that he had ever seen the kid so serious.

"He was the inventor of the guillotine, also known as The National Razor during the French revolution." Will really couldn't tell what Reid's point was, though he figured it was best to play along than try to question his motives.

"Oh, is that the thing that drops a knife down on people's heads?" Will almost winced at how dumb he sounded compared to the man sitting before him.

"Yes," Spencer said with a sliver of a smile before continuing. "And do you know why it was invented?" Reid took a long sip from his Pepsi and watched as Will slowly traced his finger along the side of his beer, attempting to think of a response.

"Uh, not really, no." He finally admitted, wondering if the actual point of this conversation was to make him feel stupid. If that was the case, Dr. Reid was doing a pretty good job.

"Well, the executions set beforehand were very… unethical. You see, depending on the criminal's social ranking, they were served different means of becoming deceased. For instance, a criminal from the lowest social ranking, the third estate, would most likely we tied down to a wheel and beaten to death with clubs and fists from a crowd of onlookers while the executioner simply watched. It would usually take the person about 3 to 4 hours to die." Reid paused, leaning down to take a sip of his Pepsi, completely ignoring how Will was staring at him like he was crazy.

"Next were the Nobility, or second estate. They were usually hung in the town center. Back then, it was fairly difficult to tell an unconscious body from a dead body, so some people had to be hung multiple times, feeling that growling need for oxygen in their chests over and over again." Will was starting to get a little freaked out. Reid was still staring at him with that intense glare as he described what sounded like a horrible way to die, almost as if he were imagining doing those same things to the man sitting across the round table.

"And the first estate, which was the highest social ranking made up of the church, were rarely ever convicted of anything. On the occasion when they were, they were usually sent to be beheaded by the executioner with an axe or sword. They would lay them down, so they were facing the floor, and the executioner would swing down the axe on the back of their neck. Usually, the axe wouldn't cut all the way through, so the criminal would have been alive as his spine was hacked away." Will didn't know what to say. His throat was dry, and his palms were sweating profusely. He rubbed them on the legs of his jeans, looking around the room frantically to avoid the doctor's glare and hopefully find JJ to come save him.

"Now Will," Reid continued, completely aware of Will's freaked-out expression. "I like you, and you seem like a good guy for JJ. But, JJ is my sister, and if you ever hurt her in any way… well, history has a funny way of repeating itself." And with a little smile, Spencer grabbed his Pepsi and stood, making his way through the crowd to where Rossi and Morgan were sitting at the bar.

"Hey Hun." JJ said excitedly as she came up behind Will. He turned, almost in slow motion, to face his girlfriend.

"Oh my god, are you okay?" Will looked like he had gone into shock, staring blankly off into space, his mouth slightly agape. He stood up slowly, taking a step toward her and-

JJ barely caught him as he fainted into her arms.

Anyways, I'm really sorry if I messed up any details about the French Revolution or any of the ways convicted felons were dealt with, I'm only in high school after all. I just really wanted to make it sound as horrifying as possible so that Will wouldn't want that to happen to him :)

P.S. – I also didn't mean to offend French people… my most sincere apologies! (Seriously, sorry!)