A/N: Well, this is it. Last chapter. (sob) Sorry it's a couple of days late, but it's about twice as long as other chapters and . . . well. . . the end was hard to write.

Thanks go to beta Stealth Dragon for all the great beta-ing for so long. And thank you to everyone for the wonderful reviews. I don't know if I would have finished this without your constant and rather vocal demands to do so. ;0)

The whole story has been a blast to write. I hope it's been a blast to read.

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"What are you talking about?" McKay asked, his voice cracking an octave high. "I don't have any idea what you're talking about."

"I know. I know you don't," Carson answered with the kind of regretful-understanding tone normally reserved for patients too delirious to realize why he was torturing them with penlights and IVs. "I'll explain when we get there."

The transporter doors slid open to a quiet, empty hallway. Carson took a cautious step out and peered around. No shots rang out. No one shouted or ran at them. "Looks clear," he said and pushed the chair forward.

McKay immediately recognized the level they were on and the direction they were heading in.

His lab.

His stomach flip-flopped with a sudden anxiety he couldn't identify. "Carson, let's go back."

"We can't, son. Michael."

"Maybe he's, uh, gone. Shifted."

"Maybe," Carson agreed. But they continued on.

Every muscle in McKay's body tensed. This was not good. "I'm not feeling right. We need to go back."

Carson slowed his stride. "What's wrong?"

McKay couldn't explain the dread that flowed through him. "I'm feeling sick."

"All right." Carson's pace picked up again. "Well, your lab's close. When we get there —"

"No!" McKay was taken aback by the vehemence — the alarm — in his own voice. Everything in him rebelled at the thought of going to his lab. "This. . . this is not a good idea. I don't know how you think you can shut the device off, Carson, but whatever you're thinking can only make things worse."

"Rodney — "

"Leave it to me. I'll figure this whole thing out."

Carson sighed. "I was going to leave it to you, lad, but we don't have time."

They were steps from the lab. McKay's hands hovered over the wheels, ready and willing to stop the chair by force if necessary. He wasn't going in that lab, and he sure as hell wasn't going to listen to what Carson had to say once they got there.

But before he had a chance to put the brakes on, the transporter doors slid open behind them. The hair on the back of his neck stood on end even as he twisted around to see who was coming.

Michael.

"Lab!" McKay shouted as Carson broke into a run. Certain death vs. unexplained anxiety? Not even a choice. "Lab!"

Stunner blasts skimmed past them, the heat brushing McKay's bare arm, his cheek, his shoulder, as they barreled down the hall and into the lab. The doors slammed shut and sealed as soon as they were all the way inside. McKay didn't know whether he or Carson had done the doors or whether their combined terror had alerted the room to impending doom, but as an inhuman howl of frustration rose in the hallway he decided it didn't matter how they were safe from the monster as long as they were safe.

"You okay?" Carson asked, winded.

"Yeah. You?" McKay realized he was equally out of breath, and he hadn't done any of the running.

"I'm okay." Carson plucked the oxygen mask from where it hung around McKay's neck. "Use this."

He complied, holding the mask to his face while Carson scouted around the room looking for something. The lab hadn't been cleaned after his team ransacked it, and the area was still strewn with papers, tablets, and tech storage boxes. McKay watched Carson's search, his stomach twisting as apprehension turned to full-blown panic.

He still didn't know why.

"What're you looking for?" he asked, his voice once again muffled behind the mask.

"The device," Carson said. He tossed aside an empty storage box.

"It's not here. You know that. Your Rodney took it with him."

Carson nodded absently, his eyes sweeping across the lab. "I suppose it's not here yet."

McKay let the mask fall back around his neck. "Yet?"

Carson looked at him, silent for a moment. Then: "How do you feel, Rodney?"

Uneasy, McKay gripped the chair's wheels and backed away a couple of inches. "Sick." The word came out plaintive. "I want to go back to the infirmary."

"Aye, I'm sure you do," Carson said, scrubbing a hand over his face. Sorrow filled his eyes. He pulled up a stool, close enough to talk but far enough away to allow McKay his personal space. "The colonel said you thought shutting the device off in one universe would affect the devices in other universes. Do you still believe that?"

The question seemed simple, but it felt like something else was going on here, something he couldn't see. A chess game he hadn't agreed to play. If he didn't know better, he'd say the question was a trap. "Yes," he answered cautiously. "I still believe that."

"And you still think once the device is off, once all the devices are off, that my Rodney, Radek, Sheppard, and Teyla will come home."

"Yes."

"Even though Radek thinks you're wrong?"

McKay's ego prickled. "Radek is the one who's wrong."

"He was right about overloading the device."

"Oh my god, they're completely two different things!" Without thinking, McKay wheeled closer. "Sure, the overload didn't work. My calculations were off. But the inter-dimensional physics are sound. You shut down one device and they all shut down, domino effect. Once they're down, everything — everyone — returns to the proper universe."

"I see."

"It's basic science," McKay insisted.

"Okay."

"Radek's an idiot."

"But you're smart enough to stop all this."

"Of course."

"Put everything back."

"Sure."

"Put everyone back."

"Yes."

"So why don't you?"

"Because you'll leave."

McKay inhaled sharply and clamped his jaws shut, horror-struck by his own words.

"Aye, my friend," Carson said softly. "That's what I thought."

-------------------------------------------------------------

It was a full minute before McKay could bring himself to speak again. It felt like an eternity.

"I didn't mean it," he said tensely, rubbing at a smear of dried blood on his palm.

"You did, lad."

McKay's head snapped up. "I didn't. You tricked me into saying that." He leaned forward, angry. "I. Didn't. Mean. It."

"I'm sorry, Rodney. I am," Carson said, sounding like he wanted to cry. "I know this came out of nowhere for you. I wanted to nudge you toward it, let you recognize it on your own. But — " he glanced worriedly at the sealed lab door "— we've run out of time."

McKay didn't respond. Couldn't respond. It felt like a weight was pressing on his chest, and it was all he could do to simply keep breathing.

His silence wasn't a problem. Carson couldn't seem to stop talking.

"I didn't realize what was going on myself until after you were injured. You talk in your sleep when you're sedated. You know that? I've never noticed it in my Rodney, but you. . . you narrated your entire dream."

McKay couldn't even muster embarrassment.

"Then you had that Freudian slip of yours. You said there were other things you could have tried besides overloading the device, but you didn't because they would have worked," Carson said. "I thought about everything that had been going on. You worked around the clock but didn't get anywhere close to a solution. You left behind a tablet PC with vital calculations when you shifted. You forcefully ignored Radek and your Samantha when they told you overloading the device wouldn't work — I think because trying something you knew will fail left everyone less time to look for something that would have worked."

Carson reached beside his stool and pulled Radek's pack onto his lap. McKay couldn't remember him taking it from the back of the wheelchair.

"And this, Rodney," Carson said, sliding out the laptop McKay had been using in the hall. "I don't think you were even fully aware you were typing this."

He flipped it open and turned the screen around.

It was list of theories, hypothetical ways to shift Carson to McKay's universe.

"You know how to stop this, how to shut down the device," Carson continued, his voice calm but insistent. "I think some part of you has always known, but you were okay with shifting, willing to let it go on because of me. Then the dimensions started to bleed together and you knew you'd have to shut it down eventually. Some part of you knew or else you wouldn't have been working on ways to get me to go with you."

They were there in black and white, words on a screen. His words. His screen. McKay squeezed his eyes shut.

"You know how to shut the device down," Carson said gently.

He shook his head.

"You do, Rodney."

Through clenched teeth McKay forced out, "I don't."

"There's a mental component to Ancient technology. Conscious or subconscious. You know that."

McKay shook his head again. He didn't want to hear this.

"Remember the personal shield, lad?" Carson asked, barely above a whisper now. "You control the device."

---------------------------------------------------------------

McKay felt disturbingly like Dorothy in the Wizard of Oz. You've always had the power. . . . .

God, he hated that movie.

"Rodney?"

McKay slowly opened his eyes. Carson had put the laptop away. He was leaning forward now, looking at him with such overwhelming sadness that McKay wanted to turn around and throw himself at the nearest Wraith because he knew what was coming next, knew what Carson was going to say and how this conversation was going to go, and he really, really did not want to do this.

"Rodney, you have to stop blaming yourself for my death."

And there it was.

"I don't," he said, flat, practiced.

Carson offered a small, rueful smile. "You may be able to lie to yourself, lad, but not to me. You're too honest to hide anything. I've said it before. It comes out in your dreams, in your actions, in — " Carson swept his arm indicating the lab, the situation, " — all of this. You carry the weight of two galaxies on your shoulders, and you have since the moment we stepped through that gate. Every loss is a personal failure. You think if you'd been smarter, faster, better —"

"Your Rodney, maybe. Not me."

"— until the guilt and what ifs eat at you." Carson paused. "I can't even imagine what my death did to you."

Like a rubber band pulled too far, something in him snapped. McKay lurched forward, propelling himself to stand. His good leg felt wobbly and his bad leg bent, threatening to crumple, but he gripped the chair for support and locked his elbows. He willed himself to stay up.

"What it did to me?" McKay spat as Carson stood, too, tensed to catch him. "What do you think? It devastated me. Devastated all of us. You died, Carson. You died and I could have stopped it by doing any one of a thousand things differently. Not even heroic things. Just my job. If I'd been doing my job as a scientist, as a friend, it never would have happened. I've had to live with that."

"Aye, you've lived with that for too long," Carson said. "You're wrong. You can't stop fate. It was horrible and tragic and believe me, I wish it hadn't happened. But you couldn't have stopped it no matter what you'd done. It was fate, lad. It wasn't you."

McKay's arms were holding virtually all his weight now and they trembled from the strain. He scowled at Carson. "Screw fate. You shouldn't have died!"

Carson scowled back. "And you shouldn't be blaming yourself!"

They stood there for a moment, glaring at each other. Then McKay's arms gave way and he pitched forward. Carson caught him, ducking under his shoulder and grabbing a fistful of the back of Ronon's shirt to keep him steady. He moved McKay to a stool next to his.

"Carson, I. . . ."

But McKay trailed off as the air shimmered around them and the empty lab was suddenly bustling with people. McKay recognized a few of scientists; most he didn't. They were oblivious to the two men on stools at the center table.

"Levels!"

"Compensating."

"We've got to —"

From the back, a Czech curse rose above the din.

Then the air shimmered again and they were gone.

-----------------------------------------------------------------

"You're waiting for the device to shift in," McKay said, astonished that it had taken him this long to put the final pieces of the puzzle together. "That's what we're doing here. You're thinking the device will shift in and I'll shut it down by. . . by wanting to. Then everything will go back to normal."

"I do."

McKay crossed his arms over his chest. "Well that's a stupid idea."

Carson raised an eyebrow. "Why? Because the device that shifts in might not be from your universe? I thought of that, but —"

McKay waved the problem away. "No, no. As long as it's from a similar enough universe, as long as I'm the one who activated it there, it'll respond to me here."

"Then what's the. . . ." Carson regarded him silently for a moment and McKay looked away. "The real problem is you still don't want to shut it down."

McKay swallowed hard. "If you're right — and I'm not saying you are — but if you're right, you're asking me to. . . to. . . ."

"Let me go."

A strangled cry escaped before McKay could fight it down. "I can't."

"Rodney," Carson said, sounding frustrated, "you're tearing apart the fabric of time and space. You have to end this."

"I can't! You'll be dead again and I . . . can't. You can't ask me to, Carson."

Then Carson was in front of him, hands on his shoulders, forcing eye contact. "I'm not your Carson, lad. I was trying to nudge you toward that realization, too. I belong in this universe. You belong in yours."

"But maybe I can —"

"You can't and you shouldn't. Don't you think I'd like to snatch your Ronon and take him along with me to live happily ever after here? But then your universe loses him and how could be content knowing I inflicted on you the same misery I was trying to avoid? You can't take me from my dimension, my friends, for the same reason. They need me."

"We need you," McKay said softly.

He braced himself for Carson to yell, to argue, to insist, "You don't need me, you selfish bastard," and storm away.

Instead, Carson pulled him up and into a hug.

"I know you do."

Stunned, McKay just stood there. Then, as his eyes watered and the tears fell, darkening the shoulder of Carson's shirt, he hugged him back.

A moment later, out of the corner of his eye, McKay caught a shimmer.

"No!" The word sounded close to a wail.

The device had shifted in.

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Sitting around the worktable, he and Carson stared at the device. Suspended in the blue force field of the container, it looked exactly like the one from his universe. Not that it mattered. He could shut it off and everything would automatically shift back to normal.

Carson was correct. He didn't believe it before, didn't want to believe it. But he could feel it now.

And that really sucked.

Carson tapped his earpiece. "Dr. Biro, please disconnect the colonel, Radek and Ronon from their IV's and other support. They'll be shifting in a moment."

Which just showed that Carson had more faith in him than he had in himself.

Off the radio, Carson looked at him. "You can do this," he said. Reading his mind again.

McKay nodded. He didn't move.

"Rodney."

McKay nodded again. "Maybe I'll, uh, get this thing working for real. You know? Look in on you. Make sure you're happy. Make sure everything's . . . okay."

Carson smiled. "I would hope you would."

McKay reached for the device. The force field crackled cool against his skin, tickling the tops of his arms as he pulled out the Ancient tech. The device hummed in his hands.

"Um," McKay started, fidgeting with the device. "So you really don't think —"

"It's not your fault your Carson's dead. I'm sure you don't believe anyone about that." Carson touched his arm and McKay looked up. "But believe me."

McKay smiled, small but genuine. "'Bye, Carson."

He closed his eyes as the device thrummed through his body, vibrating his blood, his bones, his cells faster, faster, faster until he was sure he was being torn apart.

Everything stopped.

McKay opened his eyes. He was in his own lab. Home.

Carson was gone.

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Epilogue

McKay slapped his radio as he ran toward the open wormhole. "Coming in hot!"

A bullet skimmed next to his right ear with a mosquito whine. He tucked his head to his chest and concentrated on keeping his feet pounding the ground. Blue enveloped him and an instant later he was in the gateroom, momentum propelling him forward until he stumbled from the change in ground surface and went sprawling.

The wormhole closed with a ffffttt. McKay rolled over to find Sheppard and Ronon looking down at him.

"See," he said, panting from his mad dash to the gate. "Told you I'd be right behind you."

Sheppard offered a hand and pulled him up. "Riiiight. And you've never lied about that before."

"Once, Sheppard. Once. Who do you think I got the idea from, anyway?" They headed toward the infirmary for the post mission check. "Besides, it's not like you had much choice back there. One of us had to dial the gate, one of us had to cover the gate —"

"And one of us had to be you, keeping the village's force field down long enough for us to open the gate," Sheppard finished.

McKay smirked. "A rather ingenious plan, if I do say so."

Ronon raised an eyebrow at Sheppard and shrugged reluctantly. "Gotta admit, got us back alive."

"Yeah, yeah. Got us back alive. Rodney saved the day. All hail Rodney. Blah, blah, blah," Sheppard mocked as they rounded the corner. He grinned and slapped McKay on the back. "Lunch after the mission check?"

McKay jerked a thumb in the general direction of the science labs. "Actually, I've got something I need to do. Catch you at dinner?"

"Sure," Sheppard said. "New project?"

"Old project," McKay answered. "New plan."

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The lab was empty when McKay pulled the device from the dangerous things storage unit. Radek was at lunch. His assistants were either at lunch or working out of the lab. Quiet was what McKay wanted. Solitude.

That morning, just before the mission, he'd finally figured out how to get the device to work properly.

It turned on in his hands with a click and a hum and McKay instinctively cringed. But no energy bursts blew him against the wall, no vibrations tore through his body. The device did just what it was supposed to do.

It opened a window to the next dimension.

Okay, he thought as he adjusted the device, window might be a bit melodramatic. It was more of a screen. A holographic screen that popped up from the center. As long as he touched the device, the screen followed his thoughts.

His thoughts took him to the infirmary.

He noticed Sheppard first — standing off to the side, arms folded across his chest, concern and a trace of mild amusement playing across his face. Teyla stood next to him, hands light over her round belly, hers an expression of concern alone. McKay was surprised to find them there. He figured they would have been at lunch, like his —

"Aye, I know it's a lot of blood, Rodney. Head wounds. . . ."

Carson.

He turned, looking where Sheppard and Teyla were looking. Carson at an exam bed, gloves on, gauze in hand, talking to. . . him.

Him covered in blood.

McKay blanched and stumbled back a step. It took him a moment to realize he. . . Rodney . . . was sitting up, talking, gesturing with great energy. Obviously not dead. Not dying. But blood slicked the right side of his face, wetting the collar of his t-shirt and dribbling down his arm. All that blood —

"— can't be good, Carson," Rodney finished. "This much blood should not be outside the human body."

"My thoughts exactly," McKay said, even though he knew no one could hear him or see him or even sense he was there.

"Next time zig instead of zag," Sheppard teased from the side.

McKay and Rodney turned in unison to glare at him.

"Little sympathy here!" McKay and Rodney exclaimed together, and McKay decided to stop talking now because this was just getting too creepy.

"You don't even need stitches," Sheppard said.

"I was shot in the head." Rodney emphasized, affronted.

"You were shot near your head," Sheppard corrected. "More like your ear, really."

"Yes, well, ears are important."

"Sure, for people who listen."

"Hey, you're the one who — "

Carson snapped off his gloves. "All right, lad. You're all set."

His face and arm were clean of blood. A white bandage had been placed just above and behind his ear.

Rodney blinked. "That's it?"

"You're welcome, by the way," Sheppard said with a grin. "For distracting you."

"Oh, please! You didn't —" Rodney lightly touched the bandage with a finger and looked at Carson. "Really, that's it?"

Carson smiled and tossed the gloves in the bin. "You were lucky. Another quarter centimeter and it would have cracked your skull."

"If I were really lucky, it would have been a quarter centimeter the other way and I wouldn't have been hit at all."

McKay touched the spot above his own right ear, the skin smooth and unmarked.

Rodney hopped down from the bed. "Who wants lunch?"

"Well, it's nice that getting shot in the head didn't affect your appetite," Sheppard quipped, walking with Teyla to the door.

"Nearly shot in the head," Rodney corrected with a smirk. "Carson said I was lucky. Jeez, Sheppard, keep up, will you?" He paused in the doorway and turned. "Coming, Carson?"

Like a man in a trance, Carson was staring at the bloody gauze that littered the bedside table.

"Carson?" Rodney tried again, and this time the Scot looked up, his eyes glistening and a frown twitching down the corners of his mouth. McKay's heart sank. Carson wasn't happy. Things weren't okay here.

Rodney waved Sheppard and Teyla away with "I'll catch up." Then he returned to Carson. "Hey. You okay?"

Carson nodded. "Just some bad memories creeping in."

"Ronon," Rodney immediately guessed, leaning on the end of the bed.

"Ronon."

McKay and Rodney watched silently as Carson cleaned up the mess — McKay because he didn't have a choice and Rodney because. . . well, McKay didn't know why his double wasn't saying anything. Say something consoling. Say something to cheer him up!

"You still blame yourself."

Oh.

Carson sighed. "Sometimes," he agreed, tossing the gauze into the bin and moving to strip the bed of its blood spotted sheet.

"You shouldn't, you know. Blame yourself, I mean," Rodney said. "You couldn't have saved him. No one could have. . . . "

Fate.

"I know," Carson said, draping a new sheet over the bed.

You can't stop fate.

"You did everything you could," Rodney said.

It was fate. It wasn't you.

And suddenly, watching the roles reverse in front of him, McKay understood what Carson had been trying to tell him.

"Forgiving yourself doesn't mean you forget him," Rodney said to Carson.

In his head, McKay heard Carson saying it to him.

Carson tucked the last corner in and brushed the sheet with flat of his hand, smoothing out a wrinkle. He looked up with an appreciative smile. "Aye, you're right, Rodney. I know."

Rodney shoved his hands in his pockets and nodded at the door. "So, lunch?"

"Lunch," Carson agreed.

McKay watched them go.

"Besides," Rodney said enthusiastically, "think of all the lives you have saved. Mine. Sheppard's. Teyla's. Radek's. Plus dozens more. Hundreds. Thousands."

Carson looked greatly amused. "Oh, I don't know about thousands."

"Okay, you've saved my life more than once and I've saved thousands. So technically . . . ."

They disappeared around the corner. McKay shut off the device.

He sensed Sheppard's presence before he turned.

"See what you needed?" the colonel asked from the doorway.

"Yeah," McKay said, setting the device back in its box, "I did. How'd you know?"

Sheppard strolled over. "How'd you know I was standing there?"

"Good point. We have been spending way too much time together."

Sheppard grinned. He plopped down on a stool and immediate swung it back on two legs. "So you got it working. How's. . . ."

"Good. He's good. Pretty good."

"'Pretty good?'"

"Alive." McKay paused. "With his friends."

"Good." Sheppard raised an eyebrow. "And you?"

McKay considered that for a moment. "I'm okay."

"Yeah?"

"Yeah." He met Sheppard's eyes. "Really."

Sheppard let the stool fall to all its legs and he nodded at the door. "So, lunch?"

"Lunch," McKay agreed.

"You know," Sheppard said as they headed out of the lab, "I was thinking about all the lives you've saved. Mine. Radek's. Ronon's."

"Dozens," McKay said.

"Hundreds."

"Thousands."

"Well, maybe not thousands," Sheppard said. "But you saved my life more than once and I've saved thousands."

McKay grinned at how the conversation echoed Carson's. "Then technically . . . ."

They disappeared around the corner.