On the Averrek's bridge, Zhem was following the boarding party's progress through the ship. "Status report," he said.

Ensign Tesfemarium, at the communications console, replied, "The boarding party reports that they have secured all objectives with no opposition. It appears that everyone on the ship was unprepared for the effects of the temporal distortion. Download of data is proceeding. Engineering reports that propulsion and weapons systems are now under their control. Lieutenant Rileimo is currently securing a laboratory facility that was identified as a target of opportunity."

"Very good," Zhem said.

"Commander, incoming transmission from Sucommander Khoal," Tesfemarium added. "Audio only."

"Put it on. Zhem here, Khoal. What is it?"

"Commander, we have a problem," Khoal said. "Ensign T'res now has an alternate theory about this vessel's mission."

"Put her on."

"Ensign T'res here, Commander. I am afraid we were very wrong about this vessel's purpose. This laboratory contains a large quantity of red matter."

"Red matter," Zhem repeated. "Isn't that extremely dangerous stuff?"

"Yes, Commander. There is enough red matter here to form a gravitational singularity that would completely engulf this system if ignited."

"I see. But that's not their intent."

"No, Commander, it is not. The ship is outfitted as a sleeper ship. There are enough cryogenic capsules on board to put the entire crew in suspension."

"And there's the problem, Commander," Khoal's voice added. "Ensign T'res believes - and I admit it's a logical deduction, based on what we've seen - that this vessel is intended to prevent the destruction of the Eisn system. Ambassador Spock tried to use red matter to collapse the subspace shock wave before it destroyed our worlds, but he was too late. But if this vessel goes back in time, the crew can simply find an out-of-the-way system, cloak the ship, go into stasis, and wake back up in plenty of time to save Romulus."

Zhem was silent for a long moment before he spoke. "We can let them go save our worlds, and billions of people," he said softly, "at the cost of everything we have accomplished in the last twenty-six years."

"Exactly, Commander," Khoal agreed. "And I'll be honest - I'm not so sure we should stop them."

Zhem shook his head sadly. "Khoal... Yes, maybe they could save our people. Our families, Our friends. Our homeworlds. But at what price? The Empire, and the Tal Shiar, would still rule."

"Maybe not. Things were changing in the Empire, Commander. There was a reform movement even then. My parents were part of it. My mother thought that they were only a few years away from a majority in the Senate. We could have had our Republic, on Romulus."

"Maybe..." Zhem said, his voice full of doubt.

"Commander," N'alae interrupted, "we can't. Standing orders from Fleet Command prevent any manipulation of the established timeline, for any reason. And our shipmates from Starfleet are under even stricter orders - they are required to make any sacrifice necessary to maintain the timeline."

"Understood. What has happened - happened. It's not our right to change it. But still..." Zhem looked thoughtful. "Khoal, what is the situation over there? Can we let the crew of that ship remain unconscious while we take control?"

"Ejiul is with me, Commander, and he says they have a few hours before they start to suffer neurological damage."

"Is it safe for me to beam aboard?"

"As long as you are wearing a suit with a subspace isolation field, I'd say yes, it is."

"Very good. I'll beam over as soon as I can. Meanwhile, see if you can locate the commander of that ship. I'd like to have a talk with him."

Half an hour later Zhem materialized in the engine room of the Tal Shiar ship. "Commander on deck!" one of the security guards shouted.

"Report," Zhem ordered his assembled officers.

"Ship's under our control," Eviess informed him. "We have propulsion, navigation, weapons, shields, cloak, and life support all under control from here, with the bridge locked out. If they do wake up, well, they could probably regain control eventually. But for now, this is our ship."

"And they're all unconscious," Shonna added. "The thing is, we've tried moving the unconscious ones out of here, just in case they wake up again - but a few minutes later there's some kind of temporal blip and they go right back to where they were."

"Interesting," Zhem said. "And the ship's commander?"

"We tried bringing him here," Khoal admitted. "But every time we did - well, like Shonna said, they just go back to where they were. Ensign T'res tried to explain it to me - something about a time loop that went over my head."

Zhem nodded. "Where is T'res now?"

"In the lab area. She found some data that is, apparently, fascinating. The ship's commander is in there too." Khoal gestured towards a hatchway. "Up this corridor."

"Lead on," Zhem ordered.

Halfway there they ran into Ensign Markhon and Sublieutenant Taran; Markhon was carrying the portable data storage unit. "We got it all, Commander," Markhon said with a fierce Klingon grin on his face. "We backed up their entire computer core. Our intelligence divisions are going to be very happy."

"Excellent work, Ensign," Zhem said. "Get that back to the Averrek immediately. And back it up onto a secure partition of our computer."

"Understood, Commander."

A few minutes later they entered the lab complex. Zhem took note of the cryogenic stasis pods, and eyed the red matter containment unit warily. "How did they get so much of it?" he wondered.

"They must have been working on it for years," Khoal said. "The Vulcan Science Academy claims that it took them decades to synthesize the red matter that Ambassador Spock used. If they're telling the truth."

"Well, it's highly disturbing that the Tal Shiar can do it at all," Zhem said. "Hopefully Ensign Markhon's data will shed some light on that. Where is T'res?"

"In here," Khoal said, gesturing towards a door. They entered, and found T'res engrossed in a holographic data display; it showed what looked like twisting ropes made of glowing threads.

"Commander," T'res said, coming to attention.

Zhem nodded. "This is the ship's commander?" he said, pointing at a body lying prone on the floor. The man was a heavyset Romulan, with graying hair suggesting late middle age.

"Affirmative," T'res said. "We have been unable to move him from this position for very long, due to the nature of the temporal flux this vessel is experiencing. So I have been working around him."

"Well, let's take care of that now," Zhem said. He knelt down and strapped a device onto the Tal Shiar commander's arm. "Federation remote transporter control, modified to create a subspace isolation field," he explained. "He should be regaining consciousness in a few minutes."

T'res nodded. "Then, perhaps, we can get some answers. There is a lot going on here, and I admit that I am not certain that we have the full picture yet."

Khoal gave her a curious look. "Are you over whatever spooked you earlier, Ensign?"

T'res looked slightly embarrassed. "I... apologize, Subcommander. I had difficulty maintaining my emotional control for a moment. The sight of so much red matter in the hands of the Tal Shiar frankly frightened me. And when I realized what they intended to do with it, I suffered an existential crisis. I will not allow it to happen again."

"You're afraid of what will happen if they are successful in saving Romulus?" Khoal asked.

T'res actually blushed a faint green. "Yes, Subcommander. For selfish reasons, I admit. I should not put my own existence above the lives of billions, but I did."

Zhem raised an eyebrow. "Explain."

"My parents met shortly after the destruction of Romulus, while working to construct the Ni'var refugee center on Vulcan. They were both unbonded, and they found each other - agreeable. They married, and I was born a year later. If Romulus had not been destroyed, there would have been no need for the refugee center, and it is highly probable that they would never have met." She looked down at the floor. "The prospect of having my own existence completely wiped out was unsettling."

Khoal pondered for a moment, and then said, "I don't know about you, Commander, but I'm inclined to give her a pass on this one."

"Agreed," Zhem said. "Perfectly understandable. Let's move on. What's this display that had you so fascinated, Ensign?"

The Vulcan ensign worked a few controls, and the 3-D display zoomed in to what appeared to be a double helix of glowing lines, one strand of the helix in blue, the other amber. Each strand appeared to be made up of thousands of tiny interwoven glowing hairs; occasionally a hair would break off of the main strand and loop back to rejoin lower down. Even more rarely, a hair would cross from one strand to the other.

"This is a conceptual model of multidimensional spacetime, reduced to three dimensions," T'res explained. "The amber represents the interwoven time-streams of our universe, while the blue represents what we call the Mirror universe."

"Interesting," Zhem said. "So the individual threads are?"

"Representations of individual timelines, which, when woven together, create the overall time-stream of our universe."

"And these ones that loop back and rejoin?"

"Incidents of time travel," T'res said. "And then there are the occasional crossovers between universes. But as you can see, these two universes, while largely separate, are in an entangled relationship that keeps them from diverging."

"Ah," Khoal said. "So that's why the same people keep popping up in both universes, even though the two timelines diverged centuries ago."

"Precisely," T'res said. "Each time-stream influences the course of the other, in ways that we are only just beginning to understand. The mathematical equations required to describe it are still being researched. But one thing that we are beginning to believe is that any stable time-stream requires this kind of relationship with another time-stream."

"You mean that the Mirror universe is what keeps this one stable?" Zhem sounded incredulous.

"And vice-versa," T'res said. "They mutually reinforce one another."

"Great." Khoal's voice held an edge of sarcasm. "That means we'll never be rid of them."

"Perhaps," T'res said. "But this section of the time-stream is from the twenty-first and twenty-second centuries, by the Federation calendar. Let me show you what it looks like now." She typed on the control panel, and the display changed; a new time-stream, displayed in bright violet, branched off of the amber one and began orbiting it tightly.

"This is the situation in the twenty-third century," T'res said. "based on readings of the temporal flux from that anomaly. This is what things look like after the attack on the USS Kelvin."

"Which didn't happen in our universe," Khoal said. "So this means that they did create a new, separate timeline?"

T'res nodded. "Branching off from the moment the Kelvin was attacked. That, apparently, was significant enough to create an entirely new and self-consistent time-stream."

"So now we have three," Zhem observed.

"Correct," T'res said. "And that is not a stable configuration."

"What does that mean, Ensign?"

"What that means, Commander, is hard to predict," T'res answered. "Theoretically, the most likely outcome is that after a period of instability in all three time-streams, one of the universes will separate from the other two. The two that remain entangled will reinforce each other, while the outlier, unless it can branch off its own companion universe, will decay into improbability."

"I'm not sure I want to know what 'decay into improbability' means," Zhem said. "But do you have any idea which of the three universes is most likely to suffer that fate?"

"This is speculation, Commander," T'res said. "But I would conjecture that the Mirror universe is the most likely to separate from the other two. There is a smaller but not insignificant chance that the Mirror universe and ours will maintain their current relationship, and this new, Kelvin time-stream will separate. I cannot rule out the possibility that the Mirror and Kelvin timelines will survive and ours will not, but I consider that extremely unlikely."

"Fair enough," Khoal said. "But there's still one part of this that doesn't make sense. Why attack the Kelvin? Why risk an unnecessary alteration to the timeline in the first place? Surely this ship has the ability to remain hidden from a twenty-third century Starfleet vessel. So why jeopardize their mission by destroying it?"

"We didn't," said another voice.

They all looked down at the Tal Shiar commander, who was still lying on the deck. But his eyes were now open.

"Well, Commander, I'm glad you're awake," Zhem said, extending a hand down to help the Tal Shiar commander get up. "We do have some questions to ask you."

The Tal Shiar commander ignored Zhem's hand, slowly pushing himself up to a seated position on the deck. He eyed the Republic uniforms that Zhem and Khoal were wearing, took note of T'res' Starfleet uniform, and gave the two security guards by the door a long look. Then he said, "Merak tr'Nehliann, Commander, IRW Tormhial," with an air of finality.

Zhem shook his head. "No need to be so formal, Commander," he said. "You aren't our prisoner."

Khoal raised an eyebrow, but remained silent.

"Is that so?" Commander Merak said.

Zhem nodded. "For the moment, at least, this is still a rescue mission. We observed your ship in distress, and boarded to find you and your entire crew incapacitated by a temporal anomaly. If we hadn't responded - well, my science officers tell me that the temporal anomaly will eventually expand enough to draw your ship into it. Unfortunately, the effects of the anomaly would have killed your crew by that point. Which would leave a derelict but fully armed modern warbird adrift in the past, which I think you can agree is not a good outcome. So yes, we are here to rescue you. Whether this remains merely a rescue depends very much on how you answer a few questions."

"Do you expect me to believe that?" Merak challenged. "I have been awake longer than you realize, traitor. You have managed to figure out a surprising amount on your own. But I will tell you no more."

Zhem shrugged. "Then we do it the hard way. We have your ship, we have your crew, and we have already downloaded all your data. We'll piece together a complete picture eventually. Meanwhile you'll be in a Republic prison camp."

"And it's really such a simple thing we want to know," Khoal added. "Why you want to go back in time - that I understand. I even sympathize. But we saw the Kelvin destroyed, by Romulan torpedoes. Modern Romulan torpedoes."

"It wasn't us," Merak said bitterly.

"If not you, then who?" Zhem challenged.

"I don't know," Merak admitted. "We never got a good look at the attacking vessel. But it can't have been us. If you analyze the energy signatures on those torpedoes, you'll see that they do not match any torpedoes we are carrying. So it's not us. Not now, not in the future."

Khoal snorted. "So you expect us to believe that another Romulan vessel just happened to travel back in time to the very moment that you were observing, and destroyed the ship carrying James T. Kirk's parents?"

"Kirk?" Merak sounded surprised. "Kirk was on that ship? That Kirk?"

"His parents," Zhem said. "Technically he was too, in utero."

"That explains a great deal," Merak said, deflating. "You wouldn't think destroying one random Starfleet vessel could so radically alter the course of history... but yes, that explains it."

"I think it's time we all laid our cards on the table, Commander," Zhem said. "We figured out your mission. Go back in time, sleep for a century and a half, then revive in time to stop the Hobus supernova from destroying Romulus. It's an admirable goal, if not terribly realistic. But something went wrong."

Merak sighed. "We knew that the red matter had created a temporal wormhole," he said. "But we couldn't get through it. Not from the Romulus end - that seems to have decayed. But for whatever reason, the other end of the wormhole was here. We hoped to utilize an already existing temporal anomaly to travel back in time."

T'res nodded. "I see. Since the chronitron emissions from the wormhole travel through time in all directions, you thought that you could enlarge this end of the wormhole enough to pass through it, into the past."

"Exactly," Merak said. "But it appears that another ship got pulled into the wormhole from the Romulus end when it was initially created. They wound up in the past, in this system. And when they saw a Federation target..."

"They attacked," Khoal said.

"Yes," Merak spat. "And that ruined everything."

Zhem nodded in understanding. "They created an alternate timeline. So if you pass through that wormhole now, you wind up in the past of a different universe. Nothing you do there will affect our Romulus here."

Merak sighed. "So go ahead and lock me up, Commander, for whatever crimes you want to charge me with. But my only crime is failing to save our homeworlds. Again."

"Again?"

"We've tried, so many different ways," Merak admitted. "Your Starfleet ensign there can surely tell you that there are other, more reliable ways of traveling through time. But none of them worked. We keep trying, and we keep failing."

"Perhaps not," Zhem said. He offered his hand to Merak again, who merely stared at it.

"What do you mean?"

"Commander, you can't save our Romulus, because it is already gone. We live in a world defined by its absence. And yes, that is a bitter pill to swallow, but swallow it we must. But," Zhem said, pointing at the holographic display, "there is another universe. And their Romulus isn't gone yet."

Merak looked thoughtful. Then he smiled, and reached up and took Zhem's still outstretched hand.