The return trip was handled a little differently. Gibbs grabbed Hood and stuffed him in the back seat of his truck and ordered Felix to accompany them. Felix, busy on the phone with his FBI contacts, gladly climbed into the passenger seat beside Gibbs. He had not been looking forward to another grilling by DiNozzo and David. The three younger NCIS agents spent the trip back to the Navy Yard speculating on the mysterious Agent Young.

"Man, did you notice the way Lee always calls her ma'am!" exclaimed DiNozzo.

"He must be scared stiff of her," agreed McGee. "I can't say I blame him either," he continued. "The way she laid into Dr. Hood. That was cold. I mean, they're supposed to work together, you'd think she'd have his back."

David nodded, "Indeed, she sounded like a most formidable woman. Did you notice that they both seemed to take it for granted that she could kick that Marine's ass? I don't think I'd like to get on her bad side."

"Yeah, well," said DiNozzo, "if his performance today was anything to go by, I can see why he needs a total bitch as a bodyguard. I mean, geez, I thought that Marine was gonna kill him."

By the time the three reached the Yard, Hood was deep into his research and Felix was making notes on the report of the accident that had killed Private Willis' parents. Hood was just sitting up with a grunt of approval when Ducky entered the bullpen area.

"I'm sorry to keep you waiting Jacob," the older man explained. "But I had to get Mother settled before I could leave."

"Not a problem Ducky. I needed to conduct some research first, confirm what we're looking for and I think I've done that. Plus, I think we've got some additional confirmation." Hood looked at Felix. "Tell Ducky what you found out about Private Willis' parent's deaths."

"According to the police report they died in a one-car accident. The cops first thought was a drunk-driving accident, but tox screens ruled that out. Willis' dad had a history of domestic abuse, so they considered suicide/murder. Then they did a full autopsy."

Hood smiled with satisfaction and completed Felix's sentence, "and they discovered that Willis senior died of heart failure."

Felix looked up surprised. "That's right Doc, how did you know."

Ducky looked thoughtful. "Interesting, both father and son dying of heart failure, coincidence?"

Hood shook his head. "No, I'm pretty sure that both of them suffered from either Long QT syndrome or familial atrial fibrillation."

"Of course!" exclaimed Ducky. "That would explain everything. But," he continued, "We'll have to do some genetic testing to confirm."

Hood agreed, "That's why I asked you to come in, so we could run the tests right now." The two men started toward the elevators.

"Hold on," ordered Gibbs, "what the hell are family arteries or Long QTips and what tests do you need to do? Was it natural causes?'

Hood and Ducky exchanged a quick glance. "It's your case, Jacob," murmured Ducky.

Hood cocked his head to one side. "Familial atrial fibrillations and or Long QT are heart conditions that can cause cardiac arrest and sudden death. They most often occur in people who have a mutation in their KCNE2 gene. The fact that Willis' father also died of cardiac arrest is a strong indication that they both had this genetic mutation, which is heritable.

Now this mutation is found most often in people of Ashkenazi Jewish decent, but not exclusively. And most importantly, studies have found that auditory stimulation can trigger a heart arrhythmia that, due to the low potassium levels, would lead directly to cardiac arrest. If you check my time-line, you'll see that the members of the unit all agree that Private Willis collapsed almost directly after a radio was turned on."

Gibbs' jaw dropped. "He died because the music was too loud?"

"Yeah, could be, we need to do the tests."

Gibbs headed to the elevators with the two men. "Well let's go find out."

Hood called out, "Felix, could you please bring those print-outs?"

The three young NCIS agents sat stunned. If Hood was right, then Willis did die of natural causes.

"But how did he figure it out?" David blurted out. "How did he get from too much coffee, not enough fruits to licorice and chewing tobacco to Agent Lee being startled to some obscure heart disease?"

"It's like I've been trying to tell you guys," McGee explained admiringly. "The guy's a genius; he does stuff like this all the time."

They were interrupted by the sound of the elevator opening. DiNozzo's eyes widened as he spotted a beautiful, slender blonde dressed in jeans and a t-shirt enter the area.

"Well, hello there," he said, smiling wolfishly. He extended his hand, "Very Special Agent Anthony DiNozzo at your service. May I help you?"

The blonde shot DiNozzo a look of disapproval and answered briskly, "Special Agent Rachel Young, FBI. I'm looking for Dr. Hood and Agent Lee." Rachel blinked as the three agents looked at her with their mouths hanging open.

"You're Agent Young?" DiNozzo stammered.

Rachel raised her eyebrows and nodded.

"Uh, Dr. Hood and Agent Lee are down in the morgue" McGee said, "do you want to join them?"

Rachel grimaced. "Ugh, will they have to come through here to leave?" McGee dumbly nodded. "Then if it's ok, I'll just wait here, Agent..?"

McGee pulled himself together. "I'm Tim McGee and that's" he nodded to Ziva, "is Ziva David. Why don't you sit down?" He pushed the empty chair beside his desk toward Rachel.

Rachel acknowledged the introductions with a nod and took the offered chair. She sat with a slightly amused expression on her face, well aware of the scrutiny she was under. McGee finally broke the silence.

"It's been quite an experience working with Dr. Hood. Is it true he was a Nobel candidate?"

"You heard about that? Yeah, it's true. He was nominated for the work he did on dark matter, whatever that is."

McGee was about to launch into an explanation when DiNozzo broke in.

"What I'd like to know is does he always cause this much trouble? I mean, the man sure doesn't mind who he pisses off, now does he."

Rachel smirked. "I heard Hood caused a few problems for NCIS today. Personally, I find it hard to believe that what, five federal agents, couldn't control one science geek."

"Come on," protested DiNozzo, "how could anyone expect us to control that guy? I mean, he told us he needed to ask a few questions, we never expected …."

"That he'd cause a riot?" Rachel interrupted.

The three agents gaped at her, causing Rachel to laugh outright.

"Oh, I've heard all about Quantico. You people may not know it, but my Director served in the Corps. The base commander is an old Marine buddy. He called the Director and gave him an earful after you left; then I got a call to come and see how bad things really were."

Before they could answer, the elevator doors opened again letting out a disgruntled Agent Lee. The NCIS agents looked from Young to Lee, expecting fireworks.

As soon as Felix spotted Rachel, a huge grin broke out on his face. "Agent Young! Boy am I glad to see you ma'am."

Hurrying into the bullpen, the large man pulled the smaller woman from her chair into a bear hug. The three NCIS agents tried, unsuccessfully, to keep the surprise from their faces. It was obvious that the two were genuinely fond of each other.

"Please tell me that you're gonna take the Doc off my hands? I swear, it's only been a day and he's run me ragged. I don't know how you managed him on your own for so long."

Rachel laughed. "Felix, I keep telling you, you're way too soft on him. You have to show him who's boss."

"Easier said than done," Felix huffed.

"Hmm, I do have to say that I'm disappointed in you Felix," a mock frown appeared on Rachel's face. "You let some Marine take a swing at Hood?"

"Not my fault, ma'am." He jerked his heads towards the NCIS agents. "Doc sent me to the commissary to check out some purchase records. They were supposed to be keeping an eye on him for me."

The two FBI agents turned censorious looks at the three NCIS agents.

"You let a high-priority FBI asset be assaulted?" Rachel said disapprovingly.

"What," DiNozzo protested. "How were we supposed to know that your guy would blow up at the Lieutenant?"

"I gotta say, I'm with Tony on this one," McGee added. "Sure the Lieutenant was a jerk, but, man, Dr. Hood just tore into him."

"What set Hood off?" Rachel asked sharply.

McGee shrugged, "He just lost his temper when that jerk of a lieutenant said the kid was a waste of space and better off dead."

Rachel winced, "Oh yeah, that would set him off."

The NCIS agents looked puzzled.

"Why?" asked McGee.

"The man's a biophysicist," Rachel replied coolly. "He's all about life. You tell him a life, especially a human life, isn't worth anything, you'd better duck." She shook her head. "For some reason, people always assume that just 'cause he's a genius, he can't have a temper."

Rachel looked up at Felix, her expression turning serious. "How is he? And how bad was his little episode this time?"

Felix nodded reassuringly. "He's ok; I was worried when it turned out the dead Marine was just a kid…"

"Why would that matter?" DiNozzo wanted to know.

"Boston," Rachel answered succinctly. "His last case involved the murder of infants. He takes that kind of thing hard."

"Yeah," Felix's face darkened at the memory. He shrugged, "It helped that it turned out to be natural causes. Doc feels bad for the kid, but at least what happened wasn't anyone's fault, no one did anything to the kid."

"Good," Rachel was relieved. "It sounded on the phone like Hood had his breakthrough; I assume you're done here?"

Felix smiled with satisfaction. "Yeah, we're all done. Doc and the ME confirmed that the dead Marine had some genetic thing."

"Wait a second" protested DiNozzo. "How did you know that he had it figured out? What do you mean it sounded on the phone like Hood had a breakthrough?"

Felix and Rachel exchanged smiles.

"He gets this look," Rachel began.

"And we like that look," Felix continued with sly glance at Rachel.

"Yep, cause that look means he's off on Planet Hood and just about has everything figured out. And with everything figured out, that means that you're done here."

Rachel smiled impishly. "Hood was so pissed off to be called into this case; I'm surprised he's not champing at the bit to get out of here."

"Oh he is, but I still gotta say ma'am, I'm glad you're here." Felix looked at her beseechingly. "I'd really appreciate it if you took him off my hands and talked him down."

Rachel nodded. "That's the plan. Where is he?"

"He'll be right up," Felix assured her. "Doc just sent me up here to get started on the paperwork."

Rachel raised an eyebrow. "What paperwork? This is an NCIS case. Hood was just called in to consult on the COD. As soon as I can confirm that he hasn't ruffled too many of the wrong feathers, we're outta here."

The elevator once again dinged, this time signaling the arrival of Hood and Gibbs. The two men were comparing notes when Hood looked up and saw Rachel. His face lit up and he smiled softly. "Hey, you came." He turned to Gibbs, "this is Rachel. She's my, uh, partner. Rachel, this is Agent Gibbs."

Rachel closed her eyes and shook her head, smiling at Jacob's introduction. Judging from the expressions on the faces of the NCIS personnel, she decided she needed to do some damage control before any gossip seeped out.

Rachel stepped forward and put her hand out to the man. "Special Agent Young. I'm normally the lead agent on this team." She grinned and nodded in Hood's direction. "Hope he didn't cause too many problems."

Gibbs grinned back as he took her hand. "Nah, we didn't have any problems."

Rachel arched an eyebrow. "You don't consider a near riot, disruption of the operations of a Marine base, and the assault of a high-priority FBI asset problems?"

Gibbs laughed. "Marines don't have problems, they have challenges."

Jacob scowled. "It wasn't that bad."

Rachel looked at Hood with a smile. "Ya know, Felix wasn't the only one to call me today, you really need to remember that Director Fuller served in the Corps."

"What? Frank called you?"

"Umhm," Rachel said. "He was a tad annoyed. Seems he had this crazy idea that since you were on suspension, you'd be on your best behavior. Not piss off everyone you come into contact with."

She looked at Gibbs levelly. "Seriously, the base commander read the riot act to my Director. How bad was it? What do we need to do to set things right with you and them?"

Gibbs cocked his head and regarded the woman before him. He finally answered. "Seriously? It wasn't that bad. The kid he told off, he had it coming. Yeah, the Doc here irritated a lot of people, but he did the job, found out what killed Willis. The unit can be deployed on schedule now. That will go a long way to smoothing things out."

Rachel considered this. "You suggest we let sleeping dogs lie? I can tell my Director they won't be any blow-back from either NCIS or the Marines?"

"NCIS doesn't have any problems with Dr. Hood. We asked for help and he delivered. Leon can't kick about that. As for the Marines," Gibbs shrugged. "They got what they needed. It's all good."

Rachel smiled her thanks and turned her attention to Hood. She shook her head at him in mock exasperation. "Honestly, I spend months training you in proper procedure, and what? A couple of months without me and you're running amuck in the field." She lightly ran a finger over the bruise on his cheek, "and this, if McGruder hears he may reconsider your need for a bodyguard!"

"Ow," protested Jacob, "that hurts!"

"I've seen worse," Rachel clicked her tongue. "Huh, I've had worse!"

Jacob's lips quirked upward. "Don't remind me."

Rachel smiled back. "Deal, so you ready to head out?"

"Don't we have to file a report?"

Felix smiled smugly, "Nuh, uh, Doc. No paperwork for us. This is an NCIS case; they're responsible for the paperwork."

Hood looked quizzically at Gibbs who nodded, "Sounds reasonable to me."

Rachel tilted her head and looked at her men. "So, what's the priority? Food or sleep?"

Jacob and Felix looked at each other and shrugged. They answered Rachel simultaneously.

"Sleep." said Felix.

"Food." said Jacob.

"Shall we try that again?"

Felix shook his head. "No, honestly, ma'am. I just want to head home and get some sleep."

Jacob looked concerned. "Felix, are you sure you're not too tired to drive? Do you want us to drop you off at your place?"

Felix yawned hugely. "Nah, I'm good Doc. I don't live that far from here. You go ahead with Agent Young."

Jacob opened his mouth to protest when Rachel interrupted.

"Ya know, we can't take Felix with us anyway. I brought the Mustang, he won't fit."

Jacob stiffened. "What do you mean THE Mustang?"

"Mustang?" Felix was puzzled, "what Mustang?"

Rachel turned to him enthusiastically. "Wait til you see it Felix, it's great. A 1968 Mustang convertible, sort of metallic blue with white leather interior. And it's in perfect shape."

"Hold it," interrupted DiNozzo, "You have a vintage Mustang?"

"No she doesn't," Jacob ground out.

Rachel smiled sweetly at DiNozzo, "Why yes, I do, it's outside, would you like to see it?"

"But ma'am," protested Felix, "where did you get it?"

"She stole it," snapped Jacob.

Rachel tried to keep a straight face. "I prefer to think of it as putting it into protective custody."

Felix, nodding with understanding, turned to Jacob. "A Mustang convertible? Wow, that's pretty cool Doc. How long have you had it?"

Jacob frowned. "I picked it up while I was in college."

Felix looked puzzled. "I thought you had a VW in college? That ran on vegetable oil?"

The NCIS crew blinked. A car that ran on vegetable oil?

"That one blew up my junior year." Jacob explained impatiently. "I traded the guy in the junk yard the VW for the Mustang. Over the years I've gradually restored it." He glared at Rachel. "And it's not sort of blue, it's Acapulco Blue."

"Tomato, tomayto," she replied airily. "Besides, you're a terrible driver. The real crime would be letting you behind the wheel."

Rachel started toward the elevators, Felix and Jacob falling into step on either side of her. Walking out, the two agents continued to tease Hood about his driving skills. It was obvious to the NCIS agents that, despite their initial assumptions, the agents and the scientist shared a deep bond.