Continuity note: This takes place in the middle of season 6 of NCIS and season 1 of Stargate SG-1, and the two are assumed to be roughly concurrent. It's a major disconnect in continuity, but that's where the story feels like it fits in my mind.

As always, all rights in this work are given to those who own NCIS and Stargate SG-1.

CHAPTER ONE

Leroy Jethro Gibbs stood beside his director, Leon Vance, before the big screen in MTAC. It was always a pleasure to speak with his former boss, Tom Morrow, now a director at Homeland Security, but when speaking with Morrow discomfited Vance, the pleasure was doubled.

"Did I understand you correctly, sir?" Vance asked, clearly disturbed. "You want to borrow NCIS's best team for an assignment of undetermined length at an undisclosed location?"

Morrow considered that for a brief moment. "Not entirely accurate. I am assigning Agents Gibbs, DiNozzo, and McGee to temporary duty at an Air Force installation in Colorado."

"Not Officer David?" Vance asked, and Jethro concealed his irritation at the question. There was a lot to respect about Tom Morrow, and not least was his precision.

"No," Morrow said. "Even if she weren't Mossad, she's not a U.S. citizen. Jethro - your team will report to Colonel Kennedy at Joint Base Anacostia-Bolling to be read into the assignment and receive further orders."

"When?" Jethro asked.

"An hour."

"We'll be there, sir," he said, and barely nodded to Vance before turning to head back to the bullpen.

"Appreciate you not making me call SecNav or the President, Leon." Morrow's voice faded behind him, and Jethro wondered what the foxtrot they were getting involved in now.

He loped down the stairs and toward his desk. "DiNozzo, McGee - with me."

The other two grabbed guns and gear, just as he did, and started toward the elevator - Ziva close behind.

"Not this time, Ziva," Jethro said, and she turned a frown his way.

"But -" she began.

He cut her off. "Orders."

He could tell Ziva wanted to protest, but she sat back down, scowling.

They stepped into the elevator, and Jethro waited for the doors to close before saying, "Be at Anacostia main gate in fifty minutes. Pack for a week in Colorado."

He didn't even have to turn to know that DiNozzo was grinning, and he added, "Doubt we'll have time for skiing, DiNozzo."

NCIS - SG1 - NCIS

At Anacostia, they were escorted by an airman to a windowless conference room and told to wait there. Jethro nodded acknowledgment and looked around for a coffeepot. Maybe Air Force coffee would be better than Navy coffee, but he doubted it.

"What's going on?" McGee asked.

Jethro looked at DiNozzo, who grinned slightly. "C'mon, Probie - you're supposed to be an investigator. What do you think is going on?"

"Well - uh - I think we're being sent somewhere, but where and why?"

"Pretty sure they're going to brief us on that," DiNozzo said, and took a seat at the conference table, pulling out his cell phone to tap at its keys.

"But -" McGee looked flustered, and after a sip of coffee that actually was slightly better than Navy coffee, Jethro took pity on him - a little.

"We'll know what we need to know when we need to know it," he said, and McGee nodded, once, though he still looked uncomfortable.

When they needed to know it turned out to be less than five minutes later, when the conference room door opened and a man in a colonel's uniform strode in.

"Gentlemen," he said. "Thank you for coming."

"Our pleasure," Jethro replied and glanced at the man's nametag. "Colonel Kennedy."

"Time is of the essence, so I'll be brief," Kennedy said. "You are going to a base everyone knows exists."

"Cheyenne Mountain," DiNozzo murmured, his cell phone face down on the table beside him. Jethro bit back a chuckle as McGee stared dumbfounded at the senior agent. DiNozzo just grinned.

"Yes," Kennedy confirmed. "Some things that go on there are black."

The inflection made Jethro's eyebrows lift. "More than NORAD black?"

Kennedy nodded. "You will not mention anything you see or hear there outside the black part of the base, even to personnel stationed at the complex, as not all of them are read in on the black project. You only know this much because you very likely will see black parts of the base as you do your job."

"What about Director Vance?" McGee asked.

"What about him?" Kennedy countered.

"What do we tell him?"

"He knows what he needs to know," Kennedy said. "He doesn't need to know anything else."

"Why us?" DiNozzo asked.

"Director Morrow has the utmost faith in you. I hope it's not misplaced."

DiNozzo shook his head. "I meant, why NCIS? Shouldn't AFOSI be investigating whatever happened?"

"Normally, yes," Kennedy replied. "But her death is one of the things you're investigating."

"Whoever killed her might come after us," Jethro observed.

"It's possible."

Jethro grinned. He liked a challenge. "Hoo rah."

NCIS - SG1 - NCIS

They took a sleek executive jet to Peterson Air Force Base, and Tony managed not to gush over its amenities, before they were driven to the Cheyenne Mountain Complex, passing several security checkpoints before finally pulling into an open hangar-like space. Their driver parked and escorted them to the access checkpoint, where a staff sergeant and a couple of MPs stood duty.

"Agents Gibbs, DiNozzo, and McGee," their driver announced.

The sergeant - whose name, Tony noted automatically, was Lawrence - greeted them with, "You'll need to secure all electronic gear - cell phones, laptops, smart watches - and firearms in the lockers before you go any further."

Gibbs paused, his cell phone already halfway out of his pocket. "We're not surrendering our weapons."

Sergeant Lawrence leveled a glare at Gibbs, and Tony could only hope he hid his smile at the effort. It wasn't even half as menacing as Gibbs' mildest glare. "It's part of the procedure, sir."

"There's an exception for federal law enforcement officers," Gibbs replied calmly, not in the least fazed by the man's attempt at intimidation. "Your CO can confirm that, Sergeant."

Tony didn't hear any extra inflection on the man's rank, but it was nonetheless a reminder that NCIS was here to do a job and they wouldn't be hampered.

Lawrence gestured to the desk. "Your bags, please. We can search them while the weapons issue is resolved."

It was a reasonable request, and while the sergeant picked up a phone and spoke quietly into it, Tony followed Gibbs' lead, hefting his suitcase and gear bag onto the security desk. Those four bags took up most of the desk space, and Tony stepped back while the MPs began their search of the luggage.

It was only because he'd taken those steps back that Tony saw a door at the far end of the room opening - an armored door, he noted even as he studied the man who came through it. The newcomer had medium brown hair and walked with an easy confidence that emphasized his height, taller than Gibbs but shorter than Tony himself, Tony decided as the man drew closer.

"What's the problem, Sergeant?" the man asked.

"They're refusing to surrender their firearms."

"Sounds like you need to pay more attention in your security training," the man - a colonel, Tony realized now that the eagles embroidered in blue on the shoulders of his ABU were visible. "They're federal law enforcement officers. There's an exception."

Sergeant Lawrence nodded, appearing only somewhat abashed. "Yes, sir."

"I reminded him," Gibbs observed.

"Never gonna blame a man for double-checking." The colonel held out his hand. "Jack O'Neill. Two Ls."

Gibbs took his hand. "Jethro Gibbs. Two Bs. Agents DiNozzo and McGee."

"You're clear," Lawrence said, and Tony stepped forward to retrieve his bags. Beside him, McGee hefted two suitcases and his gear bag onto the desk.

"Got your electronics secured?" O'Neill asked.

"Finishing up now," Tony answered.

A low whistle from the desk made O'Neill, Tony, and Gibbs turn. One of McGee's suitcases had been opened, and Tony wouldn't have expected it could hold the amount of electronic equipment currently on display.

"None of this goes any further," Sergeant Lawrence said. "The clothing you've used to cushion the equipment can go in the other bag, but the gear will have to be secured."

Gibbs took a step closer to get a better look, then scowled at McGee. "What's all this, McGee?"

"It's a game console," McGee said. "I always take one with me. Playing the game helps me relax."

"It's an electronic device," Sergeant Lawrence said. "It has to be secured with all the others."

"But -" McGee began.

"Into the locker," O'Neill said, and though his tone was polite, it brooked no argument.

McGee appeared to sigh silently, but stepped forward to close the suitcase.

"What's that on your wrist?" O'Neill asked, and Tony strained to get a better view.

"It's a fitness tracker," McGee said.

"Electronic device. Into the locker," O'Neill ordered then directed a baleful look toward Tony and Gibbs. "What about you two?"

Tony grinned. "Cell phone's in the locker already."

O'Neill's eyebrows shot up. "Just a cell phone?"

Gibbs shrugged. "We know it's a black op. Why would we bring anything else?"

Tony saw McGee flush as the younger agent finished securing his gear - cell phone, laptop, game console, fitness tracker - before turning back to them, but couldn't find it in himself to feel badly for the younger man. Surely he'd learned about security procedures for classified installations at FLETC, and if not there, then in his years of service at NCIS. If he hadn't, or if he hadn't been paying attention, he'd brought this on himself.

"Ready?" O'Neill asked, and Tony couldn't help but be impressed when there was only professional courtesy in the colonel's tone. If Gibbs, or even he, had asked the question, it would've been loaded with sarcasm.

Gibbs glanced over and Tony nodded. From the corner of his eye, he saw McGee nod, too. Gibbs said only, "Ready."

Tony trailed behind as they followed O'Neill to the door he'd come from. Tony wasn't surprised when O'Neill had not only to swipe a security card but also enter a code - nor when O'Neill angled his body so the numbers he pressed weren't visible - before the door opened. The door led to another corridor, then another door, and an elevator.

"I'm your liaison officer while you're here," O'Neill said when the doors to the elevator closed.

"A colonel as liaison officer?" Gibbs asked. "Seems like something a lieutenant would be assigned to."

"Yeah, well, we do things a little differently here," O'Neill replied.

"Including bringing NCIS to an Air Force investigation," Tony murmured.

"You're catching on," was all O'Neill said in response.

Anything else Tony might have said was cut off when the elevator doors opened onto what looked like a bunker out of some old 1970s movie - but then, Tony remembered that the complex had been built in the mid-60s, and it was probably advanced for its time, let alone whatever upgrades had been done in intervening decades.

They were silent while O'Neill escorted them to their quarters - not much bigger than Tony had had while agent afloat aboard the Ronald Reagan and the Seahawk, but they all had individual billets and didn't have to hot rack, so Tony wasn't complaining.

Then O'Neill escorted them to a conference room on the same level as their quarters.

"Your base while you're here," O'Neill said, and Tony followed Gibbs into the room and took a seat beside him, McGee on his other side.

"How about giving us the full briefing?" Gibbs asked.

O'Neill smirked. "The briefing you need now, at least." Then he sobered. "Four days ago, Major Lou Thomas turned up dead."

"Cause?" Gibbs asked.

"Still under investigation," O'Neill replied. "No obvious injuries and tox screen came back clean, but he was one of our team commanders, so we had OSI looking into it."

"Colonel Kennedy said the OSI agent's also dead?" Tony prompted.

"Yesterday," O'Neill said. "Her throat was cut."

"That the official cause of death?" Gibbs asked.

"So far," O'Neill replied. "The autopsy's complete, but we're still waiting for the tox screen to come back."

"Weapon?" Tony asked.

"Lying on the floor beside her."

"Fingerprints?" McGee asked, and Tony thought he sounded hopeful, almost eager.

"We sent it to the Springs for analysis," O'Neill said. "We don't have a full forensics lab here."

"So our job is to figure out who killed Major Thomas and the OSI investigator…?" Tony let the question trail off.

"Major Madison Morgan," O'Neill supplied.

"And find out if there's a connection between them," Gibbs finished for Tony. "McGee."

McGee straightened in his seat, and Tony thought he looked glad to have a task assigned to him. "If you'll show me to a computer, I can download my search algorithms and get started."

"Download?" O'Neill frowned. "From where?"

"I have a secure site in the cloud," McGee replied. "I keep all my programs there."

O'Neill shook his head. "I meant, from what computer? None of ours are connected to the Internet."

"Well, that's why I brought my laptop," McGee said. "I can use it -"

"McGee," Gibbs snapped. "You do remember we're at a black site, don't you?"

"Yes, Boss," McGee said, apparently puzzled, and Tony struggled to contain his smile.

"Your laptop isn't black," Gibbs growled. Then he glanced at Tony, and Tony took his cue - if O'Neill were liaison officer for the Air Force, then he was liaison officer for NCIS.

"I assume you have personnel files here, Colonel?" Tony asked. At O'Neill's nod, he said, "Paper or computer?"

"Bit of both," O'Neill replied.

"Can McGee have access to those?"

O'Neill considered that for a moment, then nodded. "Not a problem."

Tony smiled at the colonel. "Thanks. If you can have Major Morgan's case file on Major Thomas brought in, I'll get started."

"I want to see where both victims died," Gibbs said. "DiNozzo's taking lead on Thomas's death. I'm taking lead on Major Morgan's death."

"I'll need to talk to the other members of Major Thomas's team," Tony added, and held up a hand to forestall O'Neill's protest. "I won't ask about operational details, just behavior and relationships."

"Same here, with regard to Major Morgan's friends and coworkers," Gibbs said.

"She was OSI, Boss," Tony reminded him. "Probably didn't have a lot of friends here." He certainly hadn't had a lot of friends when he was afloat.

O'Neill surveyed them for a moment, and Tony saw a grudging respect in his expression. "I'll have the files brought in, then I'll take you to where they died. Captain Carter will escort Agent McGee to a workstation."