Note: Fair warning here; a Chemistry Major I am not. I have resorted to Internet Searches to at least attempt to make this sound realistic. However, I have discovered some really interesting tidbits that I kinda almost sorta partially understand (maybe), thanks to the fine folks at Wikipedia. I highly recommend, before reading this chapter, looking up Josiah Willard Gibbs and his contributions to Chemistry and Thermodynamics. Not only is it a really fascinating read, but it will help explain the joke that MacGyver cracks. (If ever the situation arises where you win big money on Jeopardy because of something you've read there, any contribution to either Wikipedia or the Starving Writer's Guild would be appreciated...)

Abby was waiting in the bullpen when the elevator doors opened. "How's Bishop?" she demanded, and reading the reassurance on their faces before they could even speak, she bounded forward and grabbed MacGyver's arm. "Come with me," she ordered, ignoring his bemusement as she threw a defiant look over her shoulder at the others. "Gibbs, I need him. We'll be down in my lab."

"Hang on, Abs," Gibbs ordered. "McGee, DiNozzo, report!" He held up a hand as Abby continued to tug her former mentor past Gibbs' desk. "I want him to hear this."

She heaved a sigh, letting Mac go. "Well, then… Me first! DiNozzo, make with the clicker thing!" As Tony obligingly hit the button, putting screenshots of lab results on the plasmas, Abby stepped forward. "This is from the warehouse where Andy got shot. Major Mass Spec nearly shorted out with running all of this!" she informed them, then read off a list of the chemical names.

Mac's brows rose, collided in the center of his forehead, then hooded over his dark eyes. "That's a bizarre mixture," he admitted as the others tried to interpret his expression.

"That's what I was thinking," Abby agreed. "And let me tell you, I haven't had much success trying to figure it out!"

"What do you mean?" McGee asked.

Mac leaned in closer to Abby, a conspiratorial grin lurking on the corner of his lips as he jerked his chin in Gibbs' direction. "How is he on the 'science speak'? Still a little impatient?" he asked in her ear.

"A little?!" she demanded with a giggle. Reading Mac's amusement, she faked a scowl and lowered her voice to imitate her Boss with, " 'Your point, Abs? In English?' " She squeaked and slid behind Mac's shoulder as she caught the glare Gibbs was firing at her.

"Okay, quick science lesson here," Mac said, addressing the whole team and staunchly ignoring Gibbs' irritation. "You guys know the basics of an explosion; a violent release of energy resulting from a rapid nuclear, or in this case, chemical reaction. There are chemicals that are 'reactive', meaning they cause a reciprocal change when exposed to or mixed with an outside stimulus. There are chemicals that are 'inert', meaning they are stable and nonreactive under most circumstances. What we have here is a strange mixture of mostly inert chemicals, and a few solvents that I've never seen used with them before. I couldn't tell you what the chemical reaction would be without a few experiments…" With a wince, he threw his center of gravity backwards as his words galvanized Abby into once again grabbing his arm and pulling.

"So, let's go, let's go, C'mon, Mac!" she insisted, leaning at close to a forty-five degree angle against his stance, like a five-year-old trying to tug a parent down a toy aisle.

"Abs!" Gibbs barked, his voice arctic enough to freeze her in place.

As he caught his balance, MacGyver's face split into a wide grin. "A perfect example of 'Gibbs Free Energy'… how to use temperature to induce entropy!" He seemed resigned to the fact that although Abby had dissolved into a fit of giggles, Tony and McGee were staring at him with incomprehension, and Gibbs' glare had turned increasingly frigid. "You'd have to be a chemist or a theoretical physicist to completely appreciate that humor," he said without apology.

Gibbs pursed his lips in a bid for patience. "What else?" he asked the other agents.

McGee reached for the clicker, and Tony handed it to him. "Tony and I were busy while you were gone… By the way, MacGyver, I have to commend your office at the Phoenix Foundation; they were incredibly helpful!"

"As expected, but still good to hear," Mac nodded in thanks.

"Starting with the dossier we built on Salazar, and incorporating what your team shared, we put together a list of properties owned by Salazar's companies. We found shipping manifests, and it looks like he has a load of weapons coming in to a warehouse somewhere in this area," and Tim pointed to a map that he brought up on the screen.

"ATF might be helpful in intercepting that," Mac suggested, frowning as everyone gave him a sour look. "Oh, I forgot, sorry; the Phoenix Foundation has a completely different relationship with other agencies than you guys do; we know 'our horse is bigger than their horse' and don't have to prove it. Never mind, forget I said anything!"

"Really, Mac?" Gibbs growled.

Tim rocked as Abby gave him an impatient shove. "Continuing," he said with a roll of his eyes, "We also found a whole lot of purchases that don't seem to be related to anything, coming from a bunch of his smaller companies." Another click on the remote brought invoices up on the screen. "His Industrial Waste Disposal Company just purchased twelve plastic recycling barrels. His legal-on-paper-but-nonexistent-in-reality catering company submitted an order for five cases of dish detergent. Various wires and cables were ordered by the Plumbing and Electrical Supply company."

"All legal and logical purchases for the types of businesses he 'runs'. None of this would have caught anyone's attention in and of itself; which begs the question, how did you connect it?" Mac asked.

Tony and McGee shared a proud smile. "What caught our attention was that all these purchases were made using the same delivery address," Tony explained. "When we gave this to your guys at the Phoenix Foundation, they found a few more orders that also seem disconnected." He clicked up another series of documents to the plasma screen.

Unconsciously puffing out his chest at the familiar and beloved sight of the Phoenix Foundation's logo, Mac leaned in closer to read the documents. "Why on earth would this guy 'run' a landscaping business…" He trailed off, his eyes growing wide and and worried as he read the invoice. "Uh-oh," he muttered. "That's a lot of fertilizer!"

"Why is Salazar buying fertilizer?" Gibbs demanded.

Mac paced the bull pen in a tight circle, causing Abby and Tony to move out of his way as he didn't seem to see them. "Think 'Oklahoma City', Gibbs. You can do a lot of damage with a bomb with fertilizer as its base. I've used it many times to get myself out of tight situations. The nitrites are stable by themselves, but with the right solvent and heat, they can decompose with quite a bang." The team let him think for a moment as he continued to circle the tight space between the desks. "But with the chemicals Abby found, and with the fertilizer now in the 'mix', to pardon the pun, I still can't figure out exactly what he's trying to build!"

"Which is why we need to get to the Lab!" Abby insisted, turning imploring eyes on Gibbs. She bounced happily as Gibbs nodded and waved her away. "Come on, Mac!" she said, and her smile was triumphant as he finally gave in and allowed her to drag him away.

As Mac followed her down the stairs, he had to chuckle aloud at her exuberance. She was practically running over herself with the explanations of what she'd already tried on her own. When Abby clattered to a halt outside her Lab doors and threw them open with a gracious invitation, he bowed theatrically in response and stepped inside.

"Wow, Abby… I was in here before, but didn't have a chance to look around. This is quite the setup you have!" Mac praised, taking in the extensive laboratory environment.

She grinned her thanks to the compliment, but wasn't going to let that slow them down, now that she finally had him where she wanted him. Tossing him a white lab coat and a pair of safety goggles, she led him to the stainless steel table already set up with vials, beakers, trays, and labeled cardboard cartons.

Mac picked up the clipboard with her experiment notes on it, reading it over quickly. "Still brilliant," he praised, looking up to meet her expectant gaze. Sensing her anticipation for him to continue, he picked up where he left off. As one particular blend of chemicals caught his attention, they both winced together. "Oh, I bet that smelled bad," Mac commiserated. "I did that once, out in the field. I thought I was reaching for the glass cleaner, but got the wrong bottle. I nearly suffocated myself before I could get out of there!"

That momentarily startled her, and she gave him a searching gaze. "So, not everything you try works the first time?"

"Awww, no!" he said, surprised at her response. "Sometimes what I whip up isn't strong enough to do the job I need, and I have to readjust my mixture. Sometimes it's too strong, and I destroy what I'm trying to work on. Sometimes parts fail, my timing is off, or I just can't figure out how to cobble what I need with what's in front of me."

"I thought…" she started, then trailed off uncomfortably.

"You thought 'Good Ole Clever MacGyver' always has an answer?" he guessed. "Well, the secret, Abs, is in never giving up. You can't allow yourself to be paralyzed by a momentary setback. There's always an answer… the secret is getting to it before you run out of time."

Her chin came up, and her smile put an adorable twinkle back into her emerald eyes. "Well, then, we'd better get working on this! Gibbs is going to want answers, and you know what kind of time he wants them in!" She grinned wider as Mac slipped the lab coat on, then she reached for a small remote, cued up her sound system, and set the lab rocking as they got to work.

Neither realized how much time had passed as they mixed, blended, melted, heated, and electrified the various chemical possibilities, until Gibbs came down to check on them. "It's been hours," he informed them as he breezed through the door. "What do you have?"

Mac jumped in surprise at the sound of his voice. "Ooooh," he grumbled, stretching out his shoulders. "Don't sneak up on a guy like that, especially when he has ammonium nitrate cooking! If I mix this wrong, we could all get pretty silly on Nitrous Oxide!"

"Laughing gas?" Gibbs asked in confusion.

"I hardly think he's weaponizing dental anesthesia, if that's what you're asking," Mac reassured. "I think he's aiming more for a propellant or a fuel mixture."

"Whatever this is, it's no laughing matter!" Abby informed them.

Gibbs blinked heavily. "Well?"

Mac rolled his head from side to side as he stretched his neck. "Well, we've experimented on a small scale, come up with some ideas and a few sparks and fizzles… What he's going for will definitely make a big 'boom', but he seems to be going about it the hard way." When Gibbs' tilted head and tightened eyes encouraged him to continue, he gestured to the supplies around him. "Even if you want to stay under the radar, there are easier ways to get the chemical compositions. It looks like…" Mac paused for a second to gnaw on his lower lip as his gaze swept over their experiments. "It looks like he's trying to distill the ingredients out of common products." With his lip back between his teeth, he gave a worried shrug. "Or he's making some kind of transportable chemical compound that won't be detectable by scanners, that's easy to assemble into something much uglier at a later time."

"Guesses?" Gibbs demanded. The sound of Abby ripping open another cardboard box to reveal bottles of dish soap made him look up, and he frowned as she giggled.

"Death by Dishpan Hands?" she offered, waving two of the bottles at him. His exasperation wasn't strong enough to curb her amusement as she skipped merrily back to the table.

Mac scraped a powdery white residue from one of the glass dishes under the ventilation hood. "This by itself is incredibly stable. Mix it with gasoline or alcohol…or just get it really hot… and all bets are off." A thought hit him, and he reached for another glass container. "Abs, we used the dish soap for this one here, right?" he asked, holding up the first experiment. When she nodded, he held up the second, tilting the container to emphasize the lack of white powder. "We used the basic chemical composition for this one, then? Not the actual soap itself?" Realization dawned, causing his lips to separate and his gaze to focus inward.

Gibbs took a quick step back. "I know that look!" he said in warning as Abby's concern registered. Reaching forward, he snagged her sleeve and tugged her behind him.

She peered over Gibbs' shoulder. "Yup… I do to. He's either got a brilliant idea, or this place is going up in smoke!"

Mac was mumbling to himself under his breath. "Binder? Naw, the viscosity is wrong. Maybe as a stabilizer…but no, that doesn't make sense. Maybe it's something in the…"

"Mac?" Gibbs demanded. "What?"

Focused entirely on the thought spinning through his mind, Mac reached out towards them without looking. "Got an idea, Gibbs. Abby, hand me another bottle, would you?"

She popped the lid on the bottle before offering it to him. When he touched it, he didn't grip hard enough for a secure hold, sending the bottle right through his fingers. Scrambling for a moment caused the bottle to be compressed, which coated the top with the thick blue insides. When Mac made another attempt to secure it, the bottle squirted away from him and bounced hard against the table's surface.

Flames and smoke erupted from the open containers, with a concussion powerful enough to rattle the bulletproof windows. Thick black billows filled the space, swirling to a ghastly orange color from the emergency lights as the ventilation system kicked in to draw the fumes away. Abby raced to the wall to deactivate the system before the sprinklers turned on and the Fire Department was alerted.

Gibbs coughed, groping through the clearing smoke to find Abby, and after making sure she was fine, he turned to find MacGyver huddled behind the Mass Spectrometer. "You okay?" he demanded. As Mac hacked his own lungs clear, Gibbs's concern gave way to anger. "What was that?"

Mac ignored him, scrambling back to the table to assess the damage. "Wow! Impact ignition; didn't think of that! That opens up a whole new…"

A screen flickered to life on Abby's desk, and Ducky's anxious face appeared. "Abigail! Abby, what just happened? Is everyone all right?"

Abby hurried to get in front of the camera. "Ducky, we're fine!" she assured him.

"That was quite the blast; we felt it down here!" His concern tempered slightly as he noticed Gibbs moving into view over Abby's shoulder. "Jethro! What is going on up there!"

MacGyver let out an elated yell, whirling around to share his discovery. "The inactive ingredients in the… Abby?" he interrupted himself, using his thumbs to wipe the soot from the lenses of his safety glasses. Realizing that everyone, including the Medical Examiner on the computer screen, was staring at him, he offered an embarrassed chuckle. "Oh, hi…?"

"Explain," Gibbs growled, folding his arms. "The short version," he added to forestall another chemistry lesson.

Mac pondered that for a moment, then held up the melted remains of the offending bottle of dish soap. "Cleanup on Aisle Three?"

Again, this chapter was written more for the entertainment value than from actual knowledge of Chemistry. My apologies to any Chemistry Majors out there who are currently shaking their heads at this. Also, I highly recommend that you Not Try This At Home... It makes the Condo Commandos in any housing complex a little nervous... Just Sayin'...