A Thin Line

A/N: This idea has been floating around in my head for a while. It's finally gotten on paper. YAY! I hope everyone who reads enjoys it. Thanks to REIDFANATIC for Betaing this story.

Disclaimer: I don't own Criminal Minds.

Chapter 1: A Twist

"The road to a friend's house is never long" Danish proverb

--

Reid made his way into the conference room. He sat down in one of the chairs and took one of the files from JJ. He read all the information in a matter of minutes. It was one of the benefits of being able to read twenty thousand words a minute.

"Last week, a fire broke out at a swim meet in Boston. At first, local officials thought that it was the wiring in the building. Then last night this happened." JJ pressed a button on the remote and a clip began to play. It was another swim meet, but this time the doors to the pool were locked and fire started from the water. JJ paused the clip. "Twenty people were killed and forty were seriously injured."

"Do they know what started the fire?" Morgan asked as he studied the frozen image on the screen.

"Chemicals of some kind. It is still being worked at in the lab."

"It looks like we're going need to call in a consult." Hotch said more to Gideon than the group. Gideon nodded.

"What consult?" Morgan asked. They had had cases with bombs before. They hadn't had a consult before. Why now?

"A Chemistry Professor at M.I.T. She helps out the B.A.U. with more complicated chemical bombs and fires every once and a while."

"JJ, is there a note of any kind?" Prentiss asked.

"No."

"Everyone the jet in thirty minutes." Hotch said.

--

Reid hadn't thought much of the consult that the team was going to need, until they actually arrived at the university. It was then that something occurred to Reid. Two of his best friends worked there. Reid took a sip of his coffee contemplating too many things.

"Who is this consult?" Morgan asked Hotch.

"Professor Matilda Adams." Right at that moment, Reid started to cough.

"Are you okay Reid?" Morgan asked.

"Yeah." He turned to Hotch. "Are you sure that the consult is Matilda Adams?"

"Yes. Do you know her?"

"Yeah." Reid said, with an extremely pale face.

Morgan slightly laughed. "What do you have a crush on her or something?"

"Actually, he was too busy pining over Christine Evans to even notice Mattie." A voice came from behind Reid. The team turned around to see a blonde man with a leather jacket on.

Reid looked at the man. "David! It wasn't like I was the only person hung up on Christine Evans the whole school was."

"That's true. It's good to see you man." David and Reid quickly exchanged a hug.

"Same here." Reid turned to the rest of his team. "Everyone, this is Dr. David Marks we went to college together with Matilda Adams."

"Nice to meet you." Hotch said.

"Are you heading down to Mattie's lab now?" David asked.

"Yes we are. Would you mind showing us where to go?" Gideon asked.

"Sure, I was actually heading down that way myself. I need to fix her printer again."

Reid slightly laughed. "I can't believe Mattie still has trouble with computers."

"Yeah, either can I, but they are Windows. Mattie has always been a Mac person." David said as he started to lead the team towards the lab. "Spencer, you do realize she is going to kill you if she sees the coffee right?"

"I had actually forgot about that." Reid took the last sip of his coffee before dumping the rest in the trash.

"What's with the coffee?" Morgan asked.

"Mattie has this theory that geniuses function better on tea than coffee."

"Well, how many geniuses does she know?"

"Well, she is not as smart as Spencer, but she is the only person to ever surpass him in a class. She's just one of those extremely smart people."

"Hey, is Amy still working for her?" Reid asked, changing the subject. He didn't need to be reminded of how Mattie put him in his place in that Chemistry class. It was because of Mattie that Reid never majored in Chemistry. To say the least, he still held a slight grudge against her.

"Yup."

"How old is she now?"

"Twenty-three." Reid shook his head in disbelief. He remembered meeting Amy when she had started working with Mattie. Amy was only nineteen at the time. They stopped outside a lab. "Warning, she's probably blaring music."

As they entered the lab, they discovered David was right. Pop Rock music was playing. Reid knew the song. He could not recall how though.

"I'm turning it up." The woman turning up the radio looked about twenty-three. She was thin and had short violet hair. She turned up the music and went back to the five books she was reading. Reid smiled; it was the five-book system.

The lab was nice and spacious. If anything, it looked more like a loft than an actual lab. The only things that actually made it look like a lab were the chemicals and equipment in the room.

"Reid, why don't you go ahead of us, since you know Professor Adams." Hotch said.

"Okay." Reid said.

He walked over to a woman who was in an office with a glass window in the lab. The door was already cracked open. Inside a slender brunette woman was running titrations on a few acids while also typing something into a computer. He gently walked into the room and smiled. Mattie's foot was counting out the beats of the music.

"Hey David, it's the computer in the other room that isn't printing. This one is fine."

Reid was standing directly behind Mattie and was about to touch her shoulder, but he could not help but laugh at her last comment.

Mattie knew that laugh; it was not David's. It was Spencer's laugh. She turned around, screamed, jumped up, and wrapped her legs and arms around Spencer. It was lucky that Reid did not fall down. He had not been expecting such a greeting from Mattie. "I can't believe you are here Spencer!"

"It's nice to see you too Mattie." Reid said. He felt so relaxed. It was comforting. He even closed his eyes because he was so relaxed.

The team, who was watching from the outside of the glass room, was surprised by what they saw. Reid had a woman with her arms and legs wrapped around him. "Wow." JJ said as she spoke the entire team's thoughts.

Mattie felt how Spencer's grip on her was tight. It was as if he needed her. He needed something to hold on to and for physical and emotional reasons. "Spencer… Is everything okay?" Mattie asked in almost a whisper.

"Yeah. Why wouldn't it be?" Reid lied. Mattie had always been able to tell when something was wrong with Spencer. He only hoped that she believed his lie. He thought she did when she tightened her grip on him and held him very close.

When a bell from a timer went off both Mattie and Spencer lightly jumped out of their skins. "Put me down."

Spencer instantly put Mattie down and she started to rush around her lab. She quickly replaced the neutralized acids with new acids. She put each of the neutralized acids into one of the many test tubes. Mattie then put the test tube in a machine that mixed the acids together and analyzed the solution.

The analyzed information started to flash and run on Mattie's computer. Mattie pressed the print button and the information started to print from a printer in the main lab. The woman with purple hair in the main lab grabbed the paper and started to look over the information. She went over to a white board with a bunch of equations and wrote another on the board. She started to balance it when Mattie and Spencer walked out of the lab. Mattie looked at the equation. "You're balancing the equation wrong."

"What?" The woman with purple hair asked.

"Balance everything else first. Leave the Hydrogen and Oxygen for last. Remember your basics." The woman followed Mattie's advice the equation balanced perfectly. "See."

"It's official, I hate Chemistry."

"No you don't. If you hated Chemistry, you would not do work for me."

"I should just go back to Physics."

"Well, that's always an option, but you have a Chemistry final next week. Go study."

"You're evil." The woman said as she sat down and started to read a book.

"Sure Amy." Mattie said with a smile. Mattie then looked at Hotch and the rest of the team. "Sorry to keep you waiting. How may I help you?"

Hotch put out his hand. "Hi I'm Agent Hotchner from the BAU."

"Nice to meet you Agent Hotchner. I got the call from your department right before you arrived. The message I got was very brief on details, would you mind telling me what this is about?" Mattie asked.

"There have been some chemical fires happening at swim meets in the area. The Bureau recommended you from some previous work you've done with us Dr. Adams."

"Okay. If we are going to be working together, there are a few rules I have. First, my name is Mattie. No one calls me Dr. Adams unless I am their professor. Second, if you want to play a CD it cannot be rap or hip-hop. If you have to smoke, go outside. We don't need this place blowing up."

"Is that it Dr—" Mattie had her death glare on. "Mattie. Is that all?" Hotch asked.

"Yes. I see you've met David already." Mattie turned to the woman studying. "That's Amy Long." Amy waved as she turned a page on each of the five books. She did not even look at the group. "You'll have to excuse her, she's studying for her finals."

Morgan looked at Amy. Something about her reminded him of Reid. She had that type of child innocence to her. He waved to her, but Amy just glared at him. She stood up and left the lab.

"Did I do something wrong?" Morgan asked when Amy was gone.

Mattie smiled. "No, that is Amy. She is painfully shy around strangers. It took two years for her to have a conversation with me."

Mattie turned to the rest of team, She was able to identify them all by the descriptions in the letters she had received from Spencer. He did not write as often as he used to, but she still did receive a letter, postcard, email, or call every once and awhile. Mattie knew Spencer was busy, so she was not bothered by his infrequent contacts.

After the introductions, Mattie started to ask questions about the case. With the help of Morgan talking to Garcia, Mattie was able to get a copy of the short recording of the fire. Mattie looked at the film repeatedly. The team watched Mattie. They saw how she was studying the chemical reaction that was taking place.

Mattie walked over to the white board, wiped it clean, and began to work the basics of a complex chemical equation. David and Reid were used to Mattie's behavior of getting 'trapped' in chemical equations. Reid motioned to Gideon. "She's going to be at it for awhile."

Gideon nodded. He knew what Reid meant. Gideon was able to get the attention of rest of the team and they left for the station.