Disclaimer: NUMB3RS and its associated characters, etc., belong to the show's creators and to CBS, wonderful people whom I have never met and have no connection to. I hope they don't mind me using them here; no legal infringement intended.

Spoilers: Anything from all aired episodes is fair game. This is AU in the sense that Terry is still here.

Rating: K+ - may have minor language later on, and themes I don't think kids need to worry themselves with.

Relationships: This isn't a shipper fic, but there will be some 'romantic' issues that, to tell you too much would ruin the story. But suffice it to say, it won't be Charlie/Amita. ;) We may get some D/T hints but they'll be minor.

Summary: A suspicious package delivered to the Eppes home forces Charlie to walk a mile in Don's shoes as he must investigate its origins.

Thanks: To my beta-readers! You guys are the greatest. Also to the sources from which I'm pulling information, which I'll acknowledge chapter by chapter via footnote.

Author's Note: I've noticed that at least two of the best stories out there ongoing right now for NUMB3RS are so good mostly because the people writing them really know what they're talking about and are integrating detail by writing what they know (I'm thinking of sammac's "Skewed" and Julie Cidell's "Shifting Ground"). I'm going to try to write about things I know a little about, viz. language and music, and we'll see if I can do half so well.

One thing I know nothing about is police/FBI procedures for handling suspicious packages - so I'm going to guess the best I can and if you have some advice I'd be glad to hear it. I tried to do some research but found very little. I think in real life they'd probably take it to a contained area, but I've chosen to do it this way to advance the plot.

Also, I promise subsequent chapters will have far less lengthy pre-story ramblings. :D

Pitch Perfect

by Deichtine

The doorbell rang, jerking Charlie from his state of total concentration. He rubbed the bridge of his nose and sighed, not noticing that he was leaving a pale streak of chalk dust behind. He put down the chalk, automatically wiping his hands on his pants, and skipped down the stairs, committing what he could of his train of thought to memory so as to minimize the effect of the interruption.

The man standing on his step was a UPS courier, blinking in the broad sunlight of the beautiful day, bouncing idly on his toes as he waited for the door to open. When Charlie came to the door, the man held out a small box-shaped package and a clipboard. "Delivery for Donald Eppes," he said, sounding a little bored.

Charlie accepted the package, signed for it, and brought it inside. He set it on the coffee table, making a mental note to call Don after work, and ascended the stairs again, his mind already several steps ahead, in the solarium with the chalkboard.

It wasn't until the rumbling in his stomach became too insistent to ignore that he began to notice that the light in the room was different - the sun was now shining on the opposite side of the house - and a significant amount of time had passed. He checked his watch, and was startled to see that it was well past time to start preparing supper; Dad would be home from his committee meeting for the community association soon and Charlie had promised to have supper ready.

He put his chalk down again, and stepped back to survey his work. Not bad. Larry would be pleased; so far the math was backing up his theory one hundred per cent. He picked up the little digital camera from the side table and snapped some pictures of the chalkboards, so as to be sure not to lose anything he'd done, and stretched.

"Charlie?" Don's voice came calling from downstairs, and Charlie startled mid-stretch. He hadn't heard his brother come in.

"Upstairs, Don. I'll be down in just a second." Charlie looked at his ghost-like, chalk-covered hands and decided to stop by the washroom on his way down.

"Hey, Charlie, what's this -----" Don's words were obscured by the running water.

"Just a minute Don, can't hear you." Charlie turned off the tap. "Okay, what?"

"What's this box thing?"

Charlie came down the stairs, still drying his hands on his shirt. "I don't know. It came for you this morning. UPS." Don was staring at the box as though it were a poisonous snake.

"Who from?" Don was now circling the package, bending over now and then, looking for a return address; there was none. Charlie noticed that his brother had not yet once touched the box.

Charlie shrugged. "How should I know? You know, you're around here enough already without having your mail sent here, too." He grinned to let Don know he was teasing, but Don didn't seem to hear the comment; he was motioning Charlie to shush as he held his ear closeto the box, listening.

"Well, it's not making any noise. Was it heavy?"

Charlie thought for a moment. "I don't remember. Kind of, I guess. Not excessively. Why don't you just pick it up?"

Don looked at him as if he were crazy. "Because, Charlie, I don't know what it is, who it's from, or why it's here. It could be anything, and I'm not going to move it any more than I have to. Excuse me." Don stood up and grabbed the phone. "Hi, this is Agent Don Eppes. I'm at my brother's home and I've got a suspicious package that was delivered for me at this address, and I'd like to have it checked out..." he gave the person at the other end the address and relevant information, while Charlie just stared.

"Don, don't you think you're overreacting a little? It's probably just your birthday sweater from Aunt Eliza; we got mail here for you for months after you left for university."

"It's not from Aunt Eliza. Aunt Eliza wouldn't send a sweater by UPS, and definitely not by the UPS agent you saw, who wasn't a UPS agent at all. Come on, let's move to the kitchen until they get here."

"Why do you say that?"

"Because, if there is something harmful in that package, I'd like to be away from its general vicinity."

"No, no, why do you say the guy wasn't from UPS?"

"The package was totally mislabeled. None of the correct information was there. There's no way UPS would have accepted it, much less delivered it. Did you sign for it?"

Charlie nodded. "Yeah."

Don thought for a second. "Well, I don't know what harm that could do. But we might need you to give a description of the guy."

"Well, I'll try, but I wasn't really paying attention. He interrupted me when I was working, and I barely registered his coming."

Don sighed. "Well, just think about it, remember what you can. Okay?"

Charlie nodded. He stood up, got himself and Don each a glass of water, and sat down again, and they sipped in silence, both a little tense.

"Don, do you really think that package might be dangerous?" Charlie asked at last. "Cause, you know, I just bought the house and really don't want my living room blown up yet..." The joke was half-hearted at best, but Don smiled and shook his head.

"To tell you the truth, I don't think the package itself is going to blow up, no. But I just don't think it can mean anything good. The fact that it's here, its implications worry me. If someone with a grudge against me looked me up he'd find my apartment address, right? So why was the box delivered here? Only the people who know me would know how much time I spend here."

Charlie thought about that, deeply troubled. "Are you sure it's aimed at you?"

"It was addressed to me, wasn't it?"

"But that could be meant to throw you off. Maybe it was aimed at me."

Don looked at Charlie skeptically. "Charlie, who would want to hurt you? You're a math prof, for heaven's sake, and your students like you, don't they?"

Charlie nodded. "Seem to."

"You're about as innocuous as they come. I, on the other hand, have been in charge of putting criminals behind bars, more than one for sending incendiary devices through the mail." Don stood up as the doorbell rang. "They're here. Let's find out what's in this thing."

David Sinclair led the team of Hazardous Goods personnel who entered the Eppes living room, suited and gloved. Charlie hung back, quietly observing as Don went forward to greet his teammate.

"David, man, thanks for coming. I didn't realize you were on this team."

David shrugged. "I'm not, usually. But I have the training, and Briggs was sick tonight, so I got called as backup. This the package?"

Don nodded. "That's it."

David crouched to look at it. "What tipped you off?"

"Wasn't expecting anything, certainly not here. There's no return address, and you can tell the handwriting is deliberately being disguised. The guy who brought it was dressed like UPS but it's not marked right for it. It just rang alarm bells."

David nodded. "Yeah, I can see that. Good call." Without further ado, he and his team went to work.

Most of the devices they used to check the package without opening it Charlie had never seen before, and he had to resist the urge to push in for a better look. He found it interesting to see how the FBI approached the "black box" scenario, and what methods they used to look inside without looking inside. He thought about mentioning Schrodinger's cat, thought better of it.

Finally, after much careful scanning, wiping, inch-by-inch examination, listening and other tests, David very carefully cut the tape holding the outer paper packaging together and allowed it to fall away gently, revealing a plain, polished walnut rectangular box, no more than three inches high and five wide.

"It's a music box."

Don's face betrayed his confusion, and he stepped forward to look more closely. "It's a what?"

"A music box. Give me a second and I'll show you." David examined the crack between the lid and the rest of the box, looking for any kind of leaking powder or liquid. Finding it clean, he went through the scanning procedures again. Finally, believing it to be safe, the agent wound the mechanism with the key at the back, and opened the lid.

A tinkling sound filled the suddenly quiet room, but it was not long before the expressions on the faces of the agents present turned from focussed concentration to confusion. The sound that filled the air was not truly music; there were different pitches, but the rhythm was off, and seemed to be accented oddly. Short bursts of notes were separated by brief rests.

"What the...?" David said as the sound wound down. "Did that sound like music to you?"

"Not exactly Beethoven," Don agreed. "Charlie, any ideas?" David began carefully dusting the box for fingerprints.

Charlie was surprised. Why was Don asking him? "No, I'm just as surprised as you are. Do you think the music itself might be a code?"

Don raised an eyebrow. "Well, that's kind of what I'm asking you."

Charlie shrugged. "I suppose it could be. It doesn't sound like a tune."

"You want to take it, see whether you can find a pattern there?"

"Um, don't you need to take it as evidence or something? Try to track it?"

Don shook his head. "Now that we've made sure that it's not dangerous, there's no case. Just because someone decided to send me a music box and stay anonymous - there's no actual crime in that. If they had sent me a controlled substance or a weapon, that's different, but this is just a music box, no matter how weird. So FBI resources can't really be spent on it until we have reason to believe it's attached to a larger case. As you said, this could just be some wacky present from Aunt Eliza." The tone of his voice said he thought it was anything but. "Though, if you can avoid actually taking it apart, or damaging it, it might not be a bad idea."

"Oh." David, now finished his dusting, passed the box to Charlie, who took it gingerly in the palms of his hands, feeling the grit of the leftover dust against the smoothness of the wood.

"Any prints?" Don asked, and David shook his head.

Charlie looked at his brother. "So we're on our own with this?"

"If you're willing to take a crack at it."

Charlie stared at the music box with mixed feelings. It would be an interesting problem, and a good chance to work one-on-one with Don on a project outside his work, but something just didn't feel right, something he couldn't quite define. He sighed.

"Well, okay. Why not?"

End Chapter 1.

Find a fun and interesting explanation of Schrodinger's cat at h t t p / w w w. bbc. co. uk /dna /h2g2 /A1073945 (take out all the weird spacing) - I've linked to it from my author profile too.