The explosion seemed to go on forever. Kirk pressed himself against the wall of the shaft, feeling the stone tremble against his body. Under his feet the metal stair shook violently, and he heard the shriek of tearing metal, the crack of supports snapping. Above him, a light exploded in shower of sparks; bright pricks of pain scorched his skin as darkness fell around him.

When it was over, he cautiously lifted his head and tried to assess the damage. Many of the antiquated lights were now dark, leaving the shaft even dimmer than before, but he could see that the stretch of staircase below him was simply gone, torn free of the wall by the force of the blast from the Caretaker's array. Above him...

Sh'athylnik lay sprawled across the steps, Khan kneeling beside her. Kirk's first, wild thought was that Khan had attacked her, but then he saw Khan had his fingers pressed against her neck, frowning as he checked for a pulse. Kirk staggered up to join them and reached out to touch Sh'athylnik's jaw, near her ear.

"The best place to check for a pulse on an Andorian is here," Kirk said. He could feel her heartbeat, strong and steady and deeply reassuring.

The frown cleared from Khan's face. "I see," he said.

A smear of blue darkened the white-silk hair at the back of Sh'athylnik's skull. Kirk probed the wound cautiously, mindful of what Bones would say if he overstepped the bounds of his field first-aid training, but the damage seemed superficial. She groaned faintly, but did not wake.

"Captain!"

It was Sulu, bounding recklessly down the stairs. Kirk stood up quickly. "Where are the others?" he demanded.

"Back aboard the Enterprise," Sulu said. He checked at the sight of Sh'athylnik's still body. "Is she—?"

"She's fine," Kirk said, hoping it was true. "Grab her shoulders; I'll take her feet."

Together they lifted her and began climbing the last few flights of stairs. The metal creaked alarmingly under their weight; in a few places, Kirk could see where the bolts fastening it to the wall were bent or broken. Khan trailed silently behind them. He could probably have carried Sh'athylnik alone without difficulty, but he didn't offer and Kirk didn't ask.

Kirk had one foot on the solid stone at the top of the staircase when the next bolt struck. The metal structure beneath him twisted violently, and he had just enough thought to release Sh'athylnik's feet before he dragged her down with him. Then he was falling, tumbling, as all around him metal shrieked and shattered. He rolled down half of flight of stairs, fetched up against the railing, and felt the railing give way. The dark pit of shaft yawned below him; he grabbed desperately for something, anything, and caught the edge of a riser. He flung himself back toward the safety of the wall, but a wide gap separated the edge of the staircase from the stone. Unable to check his momentum, he jerked away from the precipice and crashed down the rest of the flight of stairs. The rough metal scraped his skin bloody, and when he finally fetched up against the landing he felt something snap in his leg with a sickening stab of pain.

He lay there for a moment, the metal cold and gritty under his cheek, savoring the sensation of being alive and trying not to think about just how bad things had just become. Eventually, he forced himself to roll onto his back and figure out what had happened.

The top flight of stairs was no longer attached to the wall. It arched into the center shaft, barely anchored to the landing on which Kirk lay. Trying to climb it would send it crashing to the bottom of the shaft, and at any rate in no longer led anywhere but empty air. He eyed the wall to which it had been attached, wondering if he could climb it. The rock was rough and studded with metal bolts, and he thought he could just manage it—if his throbbing leg would let him.

He sat up gingerly and discovered he was not alone on the landing. Khan stood beside the twisted railing, studying the stair above them. It was too much to hope, he thought, that Khan might have fallen to his death. Kirk couldn't see so much as a scratch on him. He tamped down a wave of jealousy. Aside from his leg—which he suspected was broken—he ached from head to toe and could feel blood from his lacerated back soaking into the shredded remnants of his uniform. A little genetic engineering sounded tempting right now.

"Captain!" Sulu's face appeared over the edge of the stone landing above. "Are you hurt?"

"I'm fine," Kirk lied. "How's Sh'athylnik?"

"She'll have a few new bruises when she wakes up, but otherwise she's alright."

"Good. Get her up to the surface and return to the Enterprise." Another shock, distant, rocked the shaft and made the staircase above him swing wildly. "Before this place collapses around you!"

Sulu didn't move. "What about you, sir?"

"Let me worry about that—go. That's an order!"

With obvious reluctance, Sulu vanished from sight. Kirk sat back with a sigh. If the shaft collapsed and killed him, at least he would die knowing Sulu and the others were out of harm's way—and that Khan would die with him.

Belatedly, he realized he hadn't ordered Sulu not to come back once he'd delivered Sh'athylnik to the Enterprise. He considered the odds that Sulu wouldn't return with an entire rescue party, and decided they were low. It was certainly what he would do in Sulu's position. He grasped for his communicator, but it had fallen out of its pouch sometime during his tumble down the stairs. He scanned the landing, but saw only debris—and Khan, who watched him with cool eyes.

Uncomfortable under that assessing gaze, Kirk struggled to stand. Khan moved toward him, and Kirk almost reached for his phaser. But Khan only grabbed Kirk's elbow and pulled him to his feet as if he weighed nothing.

Kirk cautiously tested his bad leg, and pain shot from his calf to his spine, strong enough to make him gasp. He swayed, and would have fallen if Khan hadn't kept hold of his elbow.

"Is it broken?" Khan asked. He sounded only mildly curious, as if he didn't care on way or the other.

"I think so."

Another strike, distant this time, shook the shaft, making the staircase above them sway. Small pieces of debris rained down on them. Kirk guessed the shaft was mere minutes from collapsing; any rescue party would be nothing but a suicide mission. He pulled away from Khan's grip and looked up at the rock wall again. Khan, he felt sure, would have no trouble climbing it.

"I know you have no reason to do me any favors," he said, quickly, because he had a lot of convincing to do and not much time, "But when you get to the surface, you need to tell my crew not to send anyone down after me." A faint frown appeared between Khan's brows. Kirk didn't know if that meant he was getting through to him or not. "They won't believe you at first, but tell Spock—tell him—"

He struggled to think what would convince Spock the message had truly come from him and wasn't merely a trick on Khan's part.

"You can tell him yourself," Khan said.

Kirk gritted his teeth. This wasn't the response he expected, and he didn't have time for it. Surely Khan could see the reality of the situation? Kirk didn't think he was the kind of man who would offer a pleasant lie to spare someone's feelings.

Another blast rocked the shaft, closer than the last. The landing shook violently.

"The only way out of here is by climbing up that wall," Kirk said. "And there's no way I can make it. I can't let my people throw away their lives trying to rescue me when this shaft is about to collapse, so I need—I'm asking you to take them a message from me."

"There's no need for such heroics on you part," Khan said. "I can carry you up the wall of the shaft."

Kirk stared at him. "No, you can't."

The corners of Khan's mouth softened into an almost-smile. "I assure you, Kirk, I can."

Kirk looked up at the wall again. Without a broken leg, he could manage it. Barely. With someone hanging off his back, pulling his center of gravity backward... it would be impossible. After seeing Khan take out an entire Klingon platoon, he was willing to believe Khan might just be able to pull it off, but he wasn't willing to believe it would be easy.

"Why?" he demanded. "Why would you risk your life for me?"

Khan was silent for a long moment. A distant blast made the shaft tremble, not as strongly as last time, but somewhere a metal bolt snapped with a ping and the landing creaked. Kirk wanted to tell Khan to hurry, but he was afraid if he spoke now he would never hear the answer.

"Perhaps," Khan said, "perhaps... I believe you may be the one who can save us all."

There was nothing Kirk could say to that. Expressions of confidence from Bones and the others were one thing; they were his friends and his crew, and while Kirk would never assume such faith from them, it didn't surprise him. To hear those words from the man Kirk had tried so hard to see as nothing but a savage killer and lab-bred monster, the man he had chased across the galaxy intending to arrest or worse, was incomprehensible.

"We don't have time for this," Khan said, interrupting Kirk's thoughts. He half-turned, showing Kirk his back. "Grab my shoulders so we can get out of here."

Kirk limped over and reluctantly wrapped his arms around Khan's shoulders, like a child getting a piggy-back ride. He didn't want to get close to Khan, didn't want to owe his life to the man who had killed Admiral Pike, but wanted to die even less. Khan took his weight like it was nothing and reached for his first handhold.

The next few minutes were agony for Kirk. The only thing worse than climbing a sheer rock wall while repeated energy blasts tried to shake you off, he realized, was hanging helplessly onto another person's back while he climbed. Khan was clearly a competent climber, but Kirk's dead weight threatened to drag him backward despite his enhanced strength, and there was nothing Kirk could do about it.

Every few seconds a new blast rattled the shaft. Most of them were faint—aimed at other gaps, Kirk supposed—but a few were close enough to threaten Khan's tenuous grip. One caught Khan just as he was reaching for an especially tricky handhold. The whole shaft rocked under the impact and they skidded half a meter down the wall before Khan caught a new grip. Kirk clung desperately to Khan's back, trying not to strangle him while Khan scrabbled for footholds and falling rocks rattled off Kirk's shoulders. In the shaft behind them, the hanging segment of staircase finally tore free of the landing and careened into the darkness below.

When they were finally on solid ground again, Kirk immediately released Khan's shoulders and put some distance between them. He almost screamed in pain when he accidentally put weight on his bad leg, and then almost fell when a fresh explosion rocked the landing. Khan grabbed his arm and half-dragged, half-carried deeper into the tunnel that stretched before them. He tried to get his good leg under him, but Khan was moving too fast. Before he could protest, the tunnel behind them collapsed with a roar and a cloud of dust.

After that, Khan slowed his pace enough for Kirk to limp along, one arm around Khan's shoulders. All the lights in this section of tunnels had stopped working, but Kirk's palm-light had survived his fall and they picked their way through the falling rubble by its harsh light.

After a few twists of the tunnel, they saw half a dozen answering lights ahead of them. The lights ran forward and resolved themselves into Sulu, accompanied by McCoy and four Security personnel.

"Not that I'm not glad to see you, Mr. Sulu," Kirk said, as Bones crouched beside him and began scanning his leg, muttering under his breath, "But didn't I order you to return to the Enterprise?"

"Respectfully, sir, you didn't order me not to come back after I returned to the Enterprise."

Kirk sighed. From around his knees, Bones said, "Jim, this leg is broken."

"You don't say."

Bones stood up and dusted off the knees of his trousers. "Sarcasm won't help, you know," he said mildly. "An osteoregenerator will, but—" the tunnel shook violently "—we don't have time for that right now."

"We're almost at the top," Sulu said. "If we hurry, we might make it out alive."