Oh, this was going to be a briefing for the record books.  'Surreal' didn't even begin to describe it.

Sam leaned forward, supporting her upper body on her folded hands, and let her eyes slide to the side, surreptitiously examining the trio at the other end of the conference table. 

Daniel sat at the end, sandwiched between the elder Jacksons, who seemed unable to give up physical contact with her teammate.  Daniel still bore that round-eyed expression of overwhelmed disbelief.  All three faces were liberally streaked with tears.

Sam's belly tingled with something that she recognized vaguely as sheer delight.  This was a Good Thing, she was sure of it.

She turned her gaze back to the woman directly across the table from her.  Yet another Doctor Carter, who was looking pretty flummoxed herself as she examined the man sitting between Sam and Melburn Jackson. 

Teal'c.  Who had been one king-sized surprise to the Carter from the mirror.  Which suggested some interesting things about that alternate version of the universe.

The colonel was in Hammond's office, trying to prepare the General for this little meeting.  She'd love to hear that conversation.

Sam sternly repressed the urge to giggle, fighting against the influence of that belly-tickling semi-hysteria. 

Firmly, she reined herself in, straightening into proper military posture as the two senior officers entered the room.  Colonel O'Neill carried a steaming cup in one hand.  He leaned carefully forward between Melburn Jackson and Daniel and set the mug gently in front of the younger Jackson.  Undoubtedly coffee, their archaeologist's universal panacea. 

Daniel started and looked quickly up over his shoulder.  A bit of the helpless confusion seeped out of his expression as he nodded a silent 'thank you.'  The colonel smiled and gripped his shoulder affectionately before straightening and striding to his chair to the right of the General's.

General Hammond lowered himself into his seat with deliberate care, avoiding eye contact with the people around the table.  Once settled, he folded his hands and cleared his throat.

"Ahem.  Well…"  His pale blue eyes finally swept over the assemblage.  "It appears we once again have visitors."

'Oh, God,' she thought, the bubble of hysteria fighting to rise from her chest.  'Visitors.'

"Doctor Carter," Hammond nodded toward the Mirror-Carter.  "We've met a few of your counterparts already."

“Ah, Sir?”  Sam interrupted.  “Before we get into anything complicated, I think there’s something we need to discuss with Doctor Carter.”

He was nodding as she finished.  “Agreed, Major Carter.  And for more than one reason, you are best suited for the task.”

“Right.”  Sam sat rigidly upright and faced her image across the table.  “You need to know about entropic cascade.”

Doctor Carter tilted her neatly coifed head.  “Entropic cascade?”  Her elegant brows tweaked together as she rolled the words around her tongue.  “As in…”

Carter nodded.  “… two identical—or nearly identical—beings…”

“…the thermodynamic instability…”

“…and compatibility constraints…”

“Not to mention…”

“Yes!  And it’s cumulative…”

“…positive feedback…”

“Hey!”

“…eventual, ultimate crisis…”

“…so our mutual existence in…”

“Right.  At least…”

“Hey!  Hey, hey, hey!” 

At O’Neill’s aggravated shout, both of them jerked their heads in his direction.”

“You eggheads think you could have, like, a whole conversation here?  In English? This isn’t fun!”

“But…!”  Doctor Carter’s excitement elevated the pitch of her voice.

“Down, Doc!  We got it!  You got it.  So zip it, okay?”

Sam leaned back, grinning across the table into the answering gleam from the other Carter.  She could feel the bubbles of excited obsession fizzing in her blood.  Perfect coiffure aside, a bit of intellectual communion and she found she liked this counterpart as much as she’d come to like the first alternate Doctor Carter she’d met.  It was an unbeatable common tongue.

Hammond leaned forward over his folded hands.  “So, Doctor Carter, you understand?”

“Indeed, General.  What’s our time limit?”

“Our previous experience indicates approximately forty-eight hours.  And the incidents are… really disturbing.”  Sam grimaced.  “I really don’t want to see you go through that.  So your visit’s going to be short.”

She saw Claire’s fingers tighten over Daniel’s forearm.

“Only two days?”

“Well…”

Doctor Carter reached eagerly toward Sam.

“That would mean that the rate of stability decay would…”

“Hold it!”  The colonel’s insistent voice rose above the cacophony.  “Before you Carters manage get up to your ears in gibberish again, could someone explain… that to me?”  He gestured toward Claire.  “I mean, I know Daniel’s story, but where the hell did they come from?”

“From the alternate Earth, O’Neill,” Teal’c explained with firm patience.

O’Neill scowled at him.  “I know that, Teal’c.  But how come…”

“I’m assuming that the accident in the museum never happened in their universe, Sir,” Sam interrupted.

“Accident?”  Claire’s fingers gently stroked the muscular arm under her hand.  “It did.  I mean, there was an accident setting up our tomb exhibit.”  She turned to gaze at Daniel, her expression clearly showing how impossibly miraculous he was.  “Our baby… our Daniel was k….  He…“

Mel reached behind Daniel to grip her shoulder.  “We lost our son more than twenty-five years ago.”

Doctor Carter was staring at them in concerned confusion.  “I never realized…”

Claire slipped her hand down Daniel’s arm and slid it into his.  Gazing at their intertwined fingers, she whispered, “We never… never talked about it.  We’ve hardly mentioned his name in years.”

Sam was nodding again, bright fascination burning in her mind.  “Here, it wasn’t Daniel who was killed in that accident.  As far as we know, you, Claire, and your husband don’t have to worry about entropic cascade failure.  You… aren’t here.  You died nearly thirty years ago.”

“Dear heavens!”  Claire exchanged a glance of confusion with her husband.  “Do you mean that… hypothetically, we could… we could stay here?  Or Daniel could come back with us?”

Sam felt her lips quirk into a little smile.  “Well, we won’t let you have Daniel, but in concept, you’re right.” 

Melburn Jackson tightened his hold on Daniel's forearm.  He drew breath to speak, but Doctor Carter interrupted.

"I'm sorry, Doctor Jackson, but I'm puzzled about several rather significant things."  She was staring at the colonel, brow furrowed in confusion.  "You are Colonel Jack O'Neill, right?"

"Yep."

"So… you never took the trip?"

The colonel looked confused.  "Trip?"

"Through the Doorway?"

O'Neill arched his brows, tilting his head in his characteristic expression of sarcastic inquiry.  "Doorway?"

Doctor Carter made a sound which couldn't be called anything but a snort.  "As in 'Doorway to Heaven'?"

Sam noted that two of their three Jacksons were looking confused.

Daniel muttered, "Stargate.  Not doorway to heaven.  Stargate."

"Oh, you mean the Gate.  Yeah, I went."

She looked mildly stunned.  "But… Then you came back?"

He scowled at her.  "You sure you're really Carter?  Obviously, yes I came back."

She shook her head slightly.  "Ours didn't."

Silence.

"You mean, over there…" O'Neill's hand waved vaguely in the direction of Sam's lab.  "Over there I'm… dead."

She nodded.  "Almost certainly.  You see…"

Sam interrupted.  "Wait a second, Doctor Carter.  Let's back up and sort some things out.  I'm guessing that your version of reality is more different from ours than the others we've encountered.  For instance, Teal'c."  She smiled warmly at her team mate.  "You've never seen a Jaffa before, have you?"

"A… what?  Jaffa?"

Sam nodded.  "So you've never encountered the Jaffa."  She ticked off a counter on her finger.  "And I'm betting  you haven't met the Goa'uld, either." Another finger.

Now Doctor Carter really was looking overwhelmed.  "Ghoul?"

Sam shook her head.  "Goa'uld," she enunciated carefully.

"You know," O'Neill interjected.  "Ugly slimy snaky things that steal bodies?"

"Tell me, Doctor Carter… How long have your people been using the Gate?"

"A… about two months."

"Two months!" O'Neill exclaimed.  "We've been going through for three years.   Longer than that if you count the first Abydos trip."

"Abydos?  F… first trip?" 

Sam was definitely beginning to feel sorry for her counterpart, who was clearly overwhelmed.

"Another thing," she added.  "I'm guessing that your two archaeologists, here, don't know much about the Gate—Doorway—at all.  So that means…"

She paused.  What it probably meant was that paranoid minds had an even greater death grip on the other world's Gate than on their own.

Doctor Carter's mind was finally catching up.  "Our military keeps a very tight control over knowledge and operation of the Doorway."

"Oh, yeah."  The colonel leaned back in his chair, shaking his head in disgust.  "All that 'need to know' stuff.   Only the bozos in charge never seem to know who really does 'need to know.'"

Sam nodded.  "Doctor Carter, you're a civilian.  But I bet you've been employed on government and military projects for quite a few years."

Doctor Carter's cheeks pinked.  "Pretty much since I finished my first post-doc."

"So you're a civilian, but inside the fold.  Whereas the Jacksons are definitely outsiders.  Not just not military, but 'soft' scientists.  I'm sure they've been kept in the dark about what they were really doing, right?"

Claire spoke up for the first time.  "Yes.  We've been asked to work with some very strange artifacts and texts, but we've never been able to get anyone to explain where they came from or who found them."

Sam sat back and contemplated her counterpart.  "So, Doctor Carter.  Just how long did it take you to crack the dialing code?"

"Dialing code?  Oh, the symbols.  My team worked on it for five years before we lucked onto a combination of keys that would activate the Doorway.  It took us a while to realize the purpose of the Doorway and its relationship to the pedestal  Then, of course, the navigational issues were difficult.  We'd figured out the first six settings from the coverstone, but couldn't figure out how to factor in the directional component.  Just over nine months ago we finally got the Doorway to activate."

"Wait wait!"  Daniel leaned forward.  "Pedestal?  You had a DHD?"

"DHD?"

"The dialing device.  Umm… Dial home device."

"Oh, the SAP!  Symbol array pedestal.  Of course.  You didn't?  But how do you dial?"

"Our computer dials for us.  That explains how you can use the Gate without having had access to the Abydos cartouche and calculating for stellar drift.   So… You sent a team through the Gate nine months ago?"

"Yes.  Colonel O'Neill's team.  We never heard from them again, and can no longer connect using that symbol array.  And it took us several additional months to figure out what it was that had allowed the Doorway to connect that first time.  The home sign.  And that we could create combinations other than the one on the coverstone which would connect, as long as we added the home sign to the end of the sequence."

Sam was nodding slowly.  "The point of origin. It's also pretty evident why it took you so long, despite having a DHD.  Apparently you never figured out the significance of the seventh symbol on the coverstone."

"Seventh?  Our coverstone has only six."

Daniel's head was shaking.  "No.  Seven."

Doctor Carter’s head was shaking adamantly.  “No, the cartouche had no room for a seventh symbol.”

Sam’s head was also shaking, and she knew her smile was smug.  “Wrong.  The seventh symbol was outside the cartouche—and you never had anyone to figure it out.”

“But the how did you…”  Doctor Carter’s head was shaking more firmly.

"Ah, but ya see…" Jack's mouth quirked into a tauntingly superior smirk.  "We had something you didn't."

Silence stretched as the smirk graduated to a full grin.  "We had Daniel."

Doctor Carter's perfectly groomed eyebrow lifted.  "Excuse me?"

Sam smiled down at her folded hands.  "He said, 'We had Daniel.'  You see, your people have been making a serious mistake right from the start by keeping such a tight lid on this thing.  You really, really need your cultural experts to be on the inside.  And if you're very lucky, you've got yourselves a truly innovative thinker somewhere on your staff."  She glanced toward the end of the table.  "Maybe two."

She lifted her gaze to meet her counterpart's.  "My team had been working for two years on solving the same puzzle your people spent five years figuring out.  We didn't solve it by "lucking onto" the right combination of symbols.  Catherine Langford brought Daniel into the project, and it took him two weeks to figure it out.  And he was never told what we already knew the Stargate's purpose was."  Sam firmly held the increasingly disgruntled gaze of the other Carter.  "And it was Daniel who enabled our first exploration team to return back through the Stargate.  Or at least those who survived their encounter with Ra."

"Ra?" three voices chorused weakly.

"And that's just the beginning."  Colonel O'Neill pointed an admonishing finger at the physicist.  "You folks have barely begun to use your Gate, and you have no idea what you're playing around with.  What's out there in the universe is going to kick your butts bloody."  He snorted in self-derision.   "Shit, I'm starting to sound like the Tok'ra.  But we've come so close to biting the big one so many times it gives me Technicolor, surround sound nightmares.  And the number one reason we've survived is… Daniel."  He glanced at the large dark man sitting with quiet dignity across the table.  "And the number two reason is him."  The finger stabbed at Teal'c.  "And because your first team never returned from Abydos, and you never sent a second expedition there, you haven't met him, either.  In your universe he's still working for the big bad guys."

Doctor Carter was looking decidedly pale.  "What… I… We haven't encountered any other civilizations.  What the hell are you talking about?"

Sam leaned back, gazing at the ceiling as she thought.  “So… Your world never had a Daniel Jackson.  At least, not as an adult.  I wonder…”

O’Neill groaned.  “Please, Carter.  Don’t.”

She grinned at him, then turned back to her counterpart.  “Just think about it… There has to be a moment… a crux that splinters one universe from another.  Just maybe…”

Doctor Carter’s head tilted, her eyes vivid with speculative interest, despite the skeptical twist to her mouth.  “You think that could have been the event?”

Carter shrugged, still grinning happily.  “Who knows.  I imagine it’s pretty much impossible to really determine what sets two versions of the universe along different tracks.  But you can bet it was the crux in terms of the path the Stargate project followed.  Just look at the fallout… We’ve encountered three universes other than our own, and in every one, the program was either in the midst of disaster or heading toward it—that’s yours, by the way.” She tilted her head toward the other Carter.  “And the big difference has been the absence of Daniel.”

The General’s brows furrowed in vague annoyance. “That seems a bit extreme, Major.” 

“No, Sir.  It isn’t.  Just consider.  Daniel has shaped this project from the beginning, and in a hundred different ways.  It was his doing that got us through the Gate so quickly.  As the colonel said, it was him that made our Abydos mission a real success.  What do you want to bet that their Colonel O’Neill went through the Gate and blew the civilization of Abydos to smithereens, just as ours almost did?  And for that matter, he probably never made contact with the Abydonians at all, never actually encountered Ra, and therefore never killed Ra.  There’s every likelihood that their version of the universe still has Ra drifting around in it.”  She nodded again.  “And just remember, Sir, what happened when Apophis came through the Gate that first time.  Just what would have happened if Colonel O’Neill hadn’t been available for you to drag out of retirement?  Your people couldn’t even figure out how to fire a staff weapon.  When the first Goa’uld steps out of their Doorway, what recourse do you suppose their commanding officer is going to have?  They’ve never been visited—what are the odds that they have no iris, and thus no way to slam the door?”

O’Neill’s head was bobbing in concert with Major Carter’s, his mouth stretched into a proprietary grin as he gazed down the table at Daniel.  “Told ya,” he stage-whispered.

Major Carter smiled at her commanding officer, then turned back to the General, body inclined forward, hands gesturing excitedly.  “And that’s not nearly all.   Not even the most important difference Daniel has made.  Listen to what these people have said about their project, Sir.  Compartmentalized.  Strictly military imperatives.  No cultural or exploratory goals at all, other than the imperative to find bigger and meaner tools of war.  Granted that our program also emphasizes military objectives, but look at us.  Almost every team has some kind of cultural expert.  We have a team strictly designed to carry out negotiations.  Daniel and his people are everywhere, involved in the deepest sense in our decision-making and planning.  The major benefits we’ve gained from our use of the Stargate have been the alliances we’ve made, and they aren’t going to be making any alliances, because they aren’t going to be able to talk to anyone they meet on the other side of the Gate.  They aren’t going to try to talk.  None of that would have happened if we hadn’t had a Daniel Jackson along with us.  Even Thor, though he’s developed a somewhat… irrational… fondness for the colonel—even he was first impressed by Daniel, back on Cimmeria. ”

"Excuse me!"  Melburn Jackson was leaning forward, eager gaze locked on Sam's face.  "Did you say 'Ra'?"

"Oh, yeah," the colonel breathed.  "Living, breathing, stinkin' up the universe."

The elder Jackson twisted around to Daniel.  "Ra?"

Daniel's expression was oddly apologetic.  "Yes.  And Apophis, Heru'Ur, Osiris, Hathor…  I…I think there's a lot we need to talk about."

"Yes, I think there are quite a few things we all need to discuss."  Hammond leaned back in his chair.  "Doctor Jackson, you have the floor."

Daniel clenched his fists and took a deep breath, then stood and proceeded to explain about the Goa'uld.