The final frontier known to man, Superman thought. And somewhere in its vastness is the key to another world, other life, another civilization.

Superman was very aware of the magnitude of what he was doing. As far as he knew, it was something no man had done before.

Another man could not have breathed. Superman found that he could so aerate his lungs that he didn't need to breathe for a day or so, and could replenish easily at an oxygen-atmosphere planet, and he was fast enough always to be able to find one within the necessary time frame. Another man would have frozen to death. Superman only felt some cold. Another man would have blown apart. Superman felt some minor inner discomfort. Superhearing did nothing for him in space, but he found he could see farther than ever. And just as Zod had said, he discovered that if he strayed too far from a yellow sun for too long, the discomfort and the cold grew greater, and his sight diminished somewhat.

That didn't concern him at first. He was mostly interested in getting far out of his own galaxy. He was convinced that Krypton had to be far outside the milky way, or else Earth scientists would have gotten a hint of it. Direction was a big problem, but he decided to just pick a direction and try, and keep retrying other directions if it didn't work out. He hoped to find some clues in his journey that would help define the search better. He had nothing but time.

Actually, he had lost track of time, easy to do in space, and he really had not paid attention to how far out of his galaxy he had gone. Using superspeed used power faster and took him farther away. His first hint was the increased cold and the diminished sight. I must have been out here for a couple days, he thought. Time to start seriously looking for a yellow sun.

Normally he could easily determine the spectrum of a star if he could detect its light at all, but he had gone too far too long, and couldn't see as far as he usually could. After about a half-hour of searching, he realized he was in a dangerous situation. He felt like a swimmer who had lost sight of the shore.

Okay, any port in a storm, he thought. That's not a yellow star, but it's my best chance at finding an oxygen-atmosphere planet. And he concentrated all his effort toward a red star just within his range.

His powers seemed sluggish by the time he found an oxygen planet, and his lungs felt ready to burst. He was on the verge of blacking out when he flew into that atmosphere just in time to take a huge, gasping, gulp of air. All he could concentrate on was breathing, so it was a combination of flight and freefall that got him to the surface, and he blacked out before he landed.

"Looks like he's coming around," said the one in blue.

"What do you think, Bones? Is he going to make it?"

"I think so, Jim, but I'm damned if I can say for sure. His physiology . . . it's close to human, but with some subtle yet profound differences. He appears to have been suffocating, but the sunlight actually seems to be a factor in his recovery. Something in the spectrum is good for him."

"It's the yellow portion." Superman cleared his head and hoisted himself up on one elbow. "Thank you, gentlemen. You appear to have saved my life."

"I'm James Kirk, captain of the starship Enterprise. And you are . . . "

"Cl . . . Actually, I'm not sure what to say. Superman on the world I just came from. Kal-El on the world I hope to find."

"You just came falling out of the sky. A normal person can't do that and survive."

"Actually, I guess I'm not what you'd call a normal person in that respect. That yellow part of the spectrum, when it's dominant, enables me to fly."

"You're able to fly in space? Without a ship?" The one called Bones looked incredulous. "It sounds like a fairy tale to me."

"I come from a planet with a red sun, like this one. But when I'm under a yellow sun it makes me . . . well . . . pretty powerful."

"Fascinating." Another man in a blue shirt stepped up. But this one had pointed ears. "There is nothing in our knowledge that would account for this. In theory, a life form could be affected in this way by the varying wavelengths, but there is no such life form recorded in any of our data banks."

Kirk looked slightly amused. "Spock," he said. "You've heard the term ‘Anything is possible?' That's what it sounds like when you say ‘In theory.'"

Spock raised one eyebrow.

"This is pretty far-fetched, Kal-El or Superman or whoever you are. You have to admit that."

"I wouldn't blame you for not believing it. But I have not lost my abilities yet. It hasn't been long enough. My problem just now was lack of oxygen."

"Oh, I didn't say I don't believe it. We've seen far-fetched before. And when Spock says ‘in theory' we often discover the fact of the matter fairly soon. Actually, we could use a good theory about how to get out of the mess we're in. You'd have been a lot better off landing somewhere else."

"What do you mean?"

"Follow me and I'll show you." Kirk led him a short way up the slope, and pointed over the ridge they were standing on. There in the valley was an encampment of fierce-looking men. "Those people are Klingons. They are from a warlike planet with whom our federation has held an uneasy cease-fire for years. This particular group was trailing us in our starship, when we got trapped in a warp that pulled us - and them - into another time. We actually come from the 23rd century, and if Spock has reasoned correctly, we are probably now in the late 20th or early 21st."

"Very early 21st," said Superman.

"The Klingons followed us here, but they think we purposely led them into the warp and into this time. When we beamed down to this planet . . . "

"Beamed down?"

Kirk just looked at him. "It's a bit hard to explain. But when we came here to get some readings and confirm where and when we believe we are, they followed us and trapped us here."

"Trapped?"

"Yes. Look around. We're in a small crater."

Superman followed Kirk's gesture and saw that it was true.

"And," Kirk continued, "they have generated a force field all around it to keep us here. Try it. Stand here on the ridge and swing your arms."

Superman tried a punch, but his blow stopped before he could straighten his arm.

"They generate it from their ship. It's like a huge vertical cylinder. You fell in the top of it."

"So are they planning on keeping you here forever?"

"No. They plan to kill us, one person each day until we reveal to them the details of our plot to trap Klingons here. They're a really paranoid race. There's no plot. But we'll never convince them of that."

"Can you get someone here to help? Can you communicate with your ship?"

"Normally we could. But they ambushed us here, and overpowered us. They have our weapons and our means of communication. If we could communicate, it would be an easy matter to get out of here. All we need to do is let our crew know where we are."

"Maybe the threat to kill you is a bluff."

"It's no bluff." Kirk pointed ahead of them as they walked back down into the crater. For the first time Superman saw the dead man in the red shirt.

"Any theories, Spock?" Kirk asked as he approached his two officers.

"Captain, the only theory which seems at all worth pursuing is this Superman. It may be possible to escape if he is willing to use his powers on our behalf."

"Say no more," said Superman. "Of course I'll help." And he leaped into the air and flew against the force field barrier.

It was not like slamming against a solid object. It was more a matter of coming up against an area which sapped his strength the second he was there. Superman had no way of knowing whether being under a yellow sun would have made any difference, but somehow he thought it wouldn't. He couldn't crack the barrier.

"Maybe I could just fly you each out the top of the cylinder," he said as he approached the futuristic trio.

But it didn't work. He had the one called Bones almost outside the atmosphere, and they were still within the cylinder. These men couldn't survive being taken all the way into space. And as he landed again in the crater, his next idea was to bore a tunnel.

That didn't work, either. Although Superman was able to tunnel nearly to the core of the planet, the force field generated at least as deep as these Earth men would be able to survive. It looked hopeless.

"Superman," the doctor said to him after the tunneling attempt. "Whether you are able to save us or not, that was pretty damned impressive. It's no wonder they call you Superman."

"Thank you," Superman responded. But it didn't make him feel any better. He was obviously unable to save these men.

"Wait," he said. "How does the Klingon get in to do the killing? If I can get in physical contact with him, I can prevent it."

Kirk and Bones looked at Spock. "Their weapons operate on the same ion-field technology that their force field does," the Vulcan explained. "He can place his weapon right against it, aim, and accurately hit his target while remaining outside the barrier. It bores through anything."

"Probably not me."

"Probably?" Spock asked.

The four men were silent.

"There has to be a way," Kirk and Superman said almost at the same time.

"Sure," Bones commented. "We'll just send a telegram to Scotty and give him our coordinates."

"Coordinates?" Superman asked.

"Yes." Kirk looked up at Superman from where he was sitting. "When I mentioned beaming before, well, that same hard-to-describe process would get us safely back on our ship in a few seconds if they only knew exactly where we are."

Superman's brow wrinkled, and then smoothed out again as his features resolved slowly into a smile. He reached back into the pouch in his cape and pulled out a star chart. Then, spreading it out on the floor of the crater, blank side up, he looked up at the Starfleet officers. "I'll bet we can write with that mud over there," he said.

Spock was the only one whose expression didn't change, as the men excitedly began to scoop up mud. Starfleet officers used to the most sophisticated technology of the 23rd century were writing a message in mud.

"Our starship, the Enterprise, is orbiting this planet, Superman," Kirk said, handing him the completed message, and watching him put it back in the cape pouch. "There is no time to spare, though, because that Klingon executioner will be here any minute. Good luck."

Without a word, the man of steel shot like a bullet, straight up, out of the atmosphere, out of the cylinder.

"I'll try, sir."

Sulu looked up. "If something's happened to them . . . "

"Nothing has happened, Mr. Sulu. I'm not ready to start believin' that as yet."

"Yes, sir."

"Wait! What's that on the screen?"

Everyone's eyes grew very wide as they saw what appeared to be a human in a colorful costume floating before them in space.

"What in the name of . . . This isn't possible, is it?"

But their amazement increased when the flying man pulled a paper from his cape and spread it out before them. Right after a series of numbers that appeared to be tracking coordinates, they read a clear message: "Scotty. Beam us up."

"That can't be from them," Chekov said.

"That is from them," Scotty said. "What else have we got?" And he hurried from the bridge toward the transporter room.

"You know we have nothing to give you," Kirk responded. "If you'd only listen to reason, we could cooperate on finding our way back to our own time . . . "

"Cooperate?" the Klingon sneered.

His finger tightened on the trigger, and Kirk's throat tightened just as the tingling glow surrounded the three Starfleet officers.

"Captain!" It was Scotty, and they were in the transporter room.

"Quick, Scotty, before they beam to their own ship and are after us again. Beam in Superman."

"Superman?"

"The man who delivered our message."

"Aye, sir. He's right outside the ship." And in a couple seconds, the man of steel stood with them within the Enterprise.

"Whoa! What was that?" he said.

Kirk grinned. "An experience no one in your century has ever had, I'm sure."

There was a sudden lurch of the ship.

"What was that?"

"Unless I miss my guess, it was a photon torpedo. Superman, follow us to the bridge." Kirk and Spock and Superman moved rapidly down the starship passage, as the Enterprise was pummeled by the Klingons.

On the bridge of the Enterprise, Superman watched in fascination as Kirk skillfully took command of the firefight. The firepower and maneuverability of the two ships seemed to be an equal match, and the danger and violence of the fight were not to be minimized. Despite Kirk's skill, the Enterprise took several hits, and was in danger of being destroyed.

"The problem with Klingon ego and paranoia," Kirk said between commands, "is that they never - ever - listen. They just shoot."

Superman looked thoughtful. "You only want to get back to where you can make the time leap again, don't you?" he said.

"Yes, but we'll never make it with these maniacs on our tail."

"Can Mr. Scott beam me back out? I have an idea."

Kirk looked over at Spock, who said, "I suspect that Superman may be the means of saving us again."

"Okay. Go with Scotty."

In less than a minute, Superman was back outside the starship, flying directly toward the attacking Klingon vessel. The Enterprise crew watched in fascination as the man of steel grabbed the Klingon Bird of Prey and with his bare hands turned it in a direction where it could not aim or fire at the Federation ship. Kirk recognized his opportunity and immediately opened communication to the Klingons.

"The man who has control of your ship is our ally in this time. You are helpless in his grip. His name, appropriately enough, is Superman. You haven't a chance against him. But it is not our purpose to harm you. We only want to keep you from harming us as we return home. Coming here was an accident, not a plot, and if you wish to return to your own time, I advise you to follow us peacefully. Superman will release you when you agree. Kirk out."

After a long hesitation, the Klingon commander communicated his agreement. The silence, the calmness were startling after the maelstrom they had just experienced. And then Scotty beamed Superman back aboard the Enterprise.

"This is a historical reading of our known universe. Although I do not find a planet that fits the description of the one you came from, I do find a star that fits. And the orbiting debris suggests that there used to be a planet there that would sustain life such as yourself. This could be your destination."

"Thank you, Mr. Spock. For the first time, I now have a clear direction for my search."

"We're the ones who owe you the thanks," Kirk added. "We never would have gotten out of this alive without you, Superman. We're very grateful."

"Here, Superman," the doctor chimed in. "Keep this clipped to your belt. It will measure the amount of time away from yellow sun radiation, and warn you if you're getting to be too long without it."

"Thanks, Doctor. And I thank you for those yellow sun radiation treatments, too. I really feel charged up, now, as strong as I have ever been." Superman hesitated. "By the way, all I have ever heard Captain Kirk call you is ‘Bones'. Surely that's not your real name is it?"

The doctor smiled warmly. "No, Superman. It's Leonard McCoy."

"McCoy! Well, that's a good omen. One of my best friends on Earth is named McCoy. I seem destined to be helped by McCoys. Thank you." He turned to the other officers. "Thanks again, all of you."

Superman stepped to the transporter pad, and in a few seconds was beamed once again into space. He watched as the starship Enterprise disappeared into the anomaly that would take them to their own century. Then he turned in the direction Spock had indicated and flew off through space, the final frontier.