But their ship no longer had shields. The friction heated the hull to three hundred degrees Celsius as she brushed against the upper reaches of Threshold.

On her aft cameras Cortana saw the trailing Covenant ships open fire. Their shots followed her like a pack of predator birds.

"Come and get me," she muttered.

She adjusted the attack angle of the flagship so it nosed up, which produced a slight amount of lift. She concentrated the building heat toward the ship's tail. A turbulent wake of superheated air corkscrewed behind them.

"Cortana?" Polaski said. "We're approaching the viable edge of an exit orbit. You're getting too close to the planet."

"I am aware of our trajectory, Warrant Officer," she said and snapped off the COM. The last thing she needed was a flying lesson.

The leading edge of the plasma overtook them. It roiled in their wake, churned explosively with the atmosphere. The flagship pitched and dropped in the unstable air, but the plasma diffused and caused them no further damage. Behind the flagship was an unfurling trail hundreds of kilometers long, a wide flaming gash upon Threshold.

Cortana experienced a moment of triumph-then squelched it.

There was a new problem: The concussion from that blast had altered their flight path. The heat and overpressure wave had thinned the atmosphere ... just enough to cause the flagship to drop seven hundred meters. Wisps of ice crystals washed over the prow.

They were too deep now. They didn't have enough power to break orbit. They would spiral into the atmosphere, and would ultimately be crushed by the t.i.tanic gravitational forces of Threshold.

The Chief spun in midair and planted his feet on the "ground." The gravity had been disabled in this elevator shaft. That had made traversing the many intervening decks easy . . . as long as he'd been willing to jump and trust that the power in this part of the ship wouldn't be restored.

The Engineer clutching his shoulder tapped the tiny control panel on the wall. The doors at the bottom of the shaft sighed and slowly slid apart.

Funny how the creature didn't care what or who John was. Didn't it know their races were enemies? It was clearly intelligent and could communicate. Maybe it didn't care about enemies or allies. Maybe all it wanted to do was its job.

There was a corridor ahead, five meters wide, with a vaulted ceiling. Past a final arch, the pa.s.sage opened up into the cavernous reactor room. The ambient lights in the hallway and room were off. Along the far wall of the room, however, the ten-meterhigh reactor coils pulsed with blue-white lightning and threw hard shadows onto the walls.

The Master Chief adjusted his low-light filters to screen out the glow from the reactor. He made out the silhouettes of crates and other machinery. He also saw one of those shadows on the wall move ... with the distinct slouching waddle of a Covenant Grunt. Then the motion was gone.

An ambush. Of course.

He paused, listened, and heard the panting of at least half a dozen Grunts, and then the high-pitched uneasy squeaks the creatures emitted when they were excited.

This came as a relief to the Master Chief. If there was an Elite here, it would have maintained better discipline and silenced the Grunts.

Still, the Master Chief hesitated. His shields were gone, his armor breached. He had been fighting almost nonstop for what felt like years. He was forced to admit that he was at the limits of his endurance.

A good soldier always a.s.sessed the tactical situation-and right now, his situation was serious. A single lucky plasma shot could inflict third-degree burns along his arm and shoulder and incapacitate him, which would give the Grunts an opportunity to finish him off.

The Chief flexed his wounded shoulder, and pain lanced across his chest. He banished his discomfort and concentrated on how to win this fight.

It was ironic that after facing the best warriors in the Covenant, and after defeating the Flood, he could be killed by a handful of Grunts.

"Chief," Cortana said over the COM. "Are you there yet? I'm down to one last option."

The Master Chief replied in a whisper, "Almost."

"Be careful. Your armor is breached. You can no longer function in a compromised atmosphere."

He flashed an acknowledgment to Cortana and concentrated on the problem at hand. Using grenades was not an option; a plasma grenade or a frag near those reactor coils could breach the containment vessel.

That left stealth-and outwitting the Grunts.

Maybe he'd use his grenades after all. The Master Chief set a plasma grenade in the center of the elevator shaft. He took his remaining two frag grenades and set them aside as well. He felt along the elevator shaft walls and found what he needed-a length of hair-fine optical cord. He pulled out a three-meter length.

The Engineer gave a huff of irritation at this destruction.

The Master Chief threaded the line though the rings of his frag grenades and tied each end at anchor points ten centimeters off the floor. He wedged the grenades into the slot of the open door.

The trap was set; all he needed now was bait. He set a plasma grenade on the far wall of the shaft and triggered it.

He pushed into the corridor, fast. Four seconds to go. The gravity, still active in this portion of the ship, pulled him to the deck. He melted into the shadows and sprinted along the wall two meters farther in, and halted along the inside of the first support brace. Three seconds.

One Grunt emitted a startled cry and a plasma shot sizzled down the center of the hallway.

Two seconds.

The Master Chief pried the Engineer off his shoulder and pressed the creature firmly into the join where the brace meet the wall.

One second.

The Engineer squirmed for a moment, then stilled, perhaps sensing what was about to happen. The plasma grenade detonated. A flash of intense light flooded the hallway and the room beyond.

The rest of the Grunts cried out; plasma bolts and a hail of crystalline needles filled the pa.s.sage, impacting inside the elevator shaft.

The Grunts ceased fire. A lone Grunt cautiously stepped out from behind a crate and crept forward. It gave a barking, nervous laugh and then, encountering no resistance, waddled down the pa.s.sage toward the elevator.

Four more Grunts followed, and they pa.s.sed the Master Chief, oblivious that he hid behind the wall brace less than a half-meter from them.

They approached the elevator, sniffed, and entered.

There was the gentle ping ping as the frag grenade rings pulled free of the trip wire. The Master Chief covered the Engineer. One of the Grunts squealed, high and panicky. They all turned as the frag grenade rings pulled free of the trip wire. The Master Chief covered the Engineer. One of the Grunts squealed, high and panicky. They all turned and ran. Twin blasts of thunder enveloped the elevator shaft. Bits of meat and metal spattered along the corridor. A needier skidded to a halt a meter away. It was cracked, its energy coil dim. The Master Chief grabbed it-ducked as another plasma bolt singed over his head. He withdrew to the cover of the bracing support. He tried to activate the weapon. No luck. It was dead.

The Engineer snaked a tentacle around the weapon and tugged it away from John's grasp. It cracked the case and peeled the housing open. The tip of one of its tentacles split into a hundred needle-fine cilia and swept over the inner workings. A moment later it rea.s.sembled the weapon and handed it, grip first, to the Master Chief.

The needier hummed with energy, and the gla.s.sine quills the weapon fired glowed a cool purple.

"Thanks," he whispered.

The Engineer chirped.

The Master Chief edged around the brace. He waited, needier held tightly in his hand, and became completely still. He had all the time in the world, he told himself. No need to rush. Let the enemy come to you. All the time- A Grunt poked its nose over a crate, trying to spot its enemy; it took a blind shot down the corridor and missed.

The Master Chief remained where he was, raised the needier, and fired. A flurry of crystal shards propelled down the pa.s.sage and impaled the Grunt. It toppled backward, and the shards detonated.

The Master Chief waited and listened. There was nothing except the gentle thrumming of the reactor.

He moved down the corridor, weapon held before him as he cleared the room. He was careful to watch for the faint rippling of air that would alert him to the presence of camouflaged Elites. Nothing.

The Engineer floated behind him, and then accelerated toward the disengaged power coupling. It hissed and chittered as it rapidly manipulated a small square block of optical crystal, unscrambling the internal circuit pathways.

"Cortana," he said. "I've gotten to the coupling. The Engineer appears to know what it's doing. You should have power for the Slips.p.a.ce generator in a moment."

"It's too late," Cortana told him.

CHAPTER NINE.

1827 hours, September 22,2552 (Military Calendar) Aboard unidentified Covenant flagship, uncharted system, Halo debris field.

The flagship plunged through Threshold's churning atmosphere. Cortana could not hold the ship's att.i.tude. It wobbled and blasted a fiery scar through the clouds, slowly rolling to port on its central axis.

Without shields, the flagship's hull continued to heat to seventeen hundred degrees Celsius. The nose glowed a dark red, which spread into an amber smear along the midsection and became a white-hot plume at the ship's tail. Conduits and feathery antenna arrays melted, separated, and left a trail of molten metal in an explosive wake. Shocks rippled along the frame as the overpressure shed off the bow in waves. The friction from the planet's dense atmosphere would shred the ship in a matter of seconds.

"Cortana," the Master Chief said. "I've gotten to the coupling. The Engineer appears to know what it's doing. You should have power for the Slips.p.a.ce generator in a moment."

"It's too late," Cortana told him. "We are now too low to escape Threshold's gravitational pull. Even at full power we can't break our degrading orbit. And we can't tunnel into Slip-s.p.a.ce, either."

The incoming Covenant fire had forced them deeper into the atmosphere. She had pushed their trajectory to the edge of what had been safe-it was that, or be engulfed in plasma. But she had saved them from one death ... only to delay that fate by a scant minute.

She recomputed the numbers, thrust and velocity and gravitational attractions. Even if she overloaded the reactors to critical-meltdown levels, they were still stuck in an ever-descending spiral. The numbers didn't lie.

The Master Chief's Engineer must have repaired the power coupling, because the Slips.p.a.ce generator was functional again- for all the good it did them.

To enter Slips.p.a.ce a ship had to be well away from strong gravitational fields. Gravity distorted the superfine pattern of quantum filaments through which Cortana had to compute a path. Covenant Slips.p.a.ce technology was demonstrably superior, but she doubted that the enemy had ever attempted a Slips.p.a.ce entry this close to a planet.

Cortana toyed with the idea of trying anyway-pulse the Slip-s.p.a.ce generators and maybe she'd get a lucky quadrillion-to-one shot and locate the correct vector through the tangle of gravity-warped filaments. She rejected the possibility; at their current velocity, any attempt to maneuver the ship would send it into a chaotic tumble from which they'd never recover.

"Try something," the Chief said to her with amazing calm. "Try anything."

Cortana sighed. "Roger, Chief."

She booted the Covenant Slips.p.a.ce generators; the software streamed through her consciousness.

The UNSC Shaw-Fujikawa Slips.p.a.ce generators ripped a hole in normal s.p.a.ce by brute force. But the Covenant technology used a different approach. Sensors came online, and Cortana could actually "see" the interlacing webs of quantum filaments surround the flagship.

"Amazing," she whispered.

The Covenant could pick a path through the subatomic dimensions; a gentle push from their generators enlarged the fields just enough to allow their ships to pa.s.s seamlessly into the alternate s.p.a.ce with minimal energy. Their resolution of the reality of s.p.a.ce-time was infinitely more powerful than human technology. It was as if she had been blind before, had never seen the universe around her. It was beautiful.

This explained how the Covenant could make jumps with such accuracy. They could literally plot a course with an error no larger than an atom's diameter.

"Status, Cortana?" the Master Chief asked.

"Stand by," she said, annoyed at the distraction.

At this resolution Cortana could discern every ripple in s.p.a.ce caused by Threshold's gravity, the other planets in this solar system, the sun, and even the warping of s.p.a.ce caused by the ma.s.s of this ship. Could she compensate for those distortions?

Pressure sensors detected hull breaches on seventeen outer decks. Cortana ignored them. She shut down all peripheral systems and concentrated on the task at hand. It was their only way out of this mess: They'd get out out by going by going through. through.

She concentrated on interpolating the fluctuating s.p.a.ce. She generated mathematical algorithms to antic.i.p.ate and smooth the gravitational distortions.

Energy surged from the reactors into the Slips.p.a.ce generator matrices. A path parted directly before them-a pinhole that became a gyrating wormhole, fluxing and spinning.

Threshold's atmosphere throbbed and jumped through the hole-sucked into the vacuum of the alternate dimension.

Cortana dedicated all her runtime to monitoring the s.p.a.ce around the ship, and risked making microscopic course corrections to maneuver them into the fluctuating path. Sparks danced along the length of the hull as the nose of the flagship departed normal s.p.a.ce.

She eased the rest of the ship through, surrounded by whirling storms and jagged spears of lightning.

She pinged her sensors: The hull temperature dropped rapidly and she registered a series of explosive decompressions on the breached decks.

Cortana emerged from her coc.o.o.n of concentration and immediately sensed the electronic presence of the other near her, monitoring her Slips.p.a.ce calculations. It was practically on top ofher.

"Heresy!" it hissed and then withdrew... and vanished. Cortana pulsed a systems check along every circuit in the ship, hoping to track the Covenant AI. No luck. "Sneaky little b.a.s.t.a.r.d," she broadcast throughout the system. "Come back here."

Had it seen what she had done? Had it understood what she'd just accomplished? And if so, why declare it a "heresy"?

True, manipulating eighty-eight stochastic variables in eleven-dimensional s.p.a.ce-time was not child's play... but it was possible that the other AI would be able to follow her calculations.

Perhaps not. The Covenant were imitative, imitative, not innovative; at least, that's what all the ONI intelligence gathered on the collection of alien races had reported. She had thought this was exaggeration, propaganda to bolster human morale. not innovative; at least, that's what all the ONI intelligence gathered on the collection of alien races had reported. She had thought this was exaggeration, propaganda to bolster human morale.

Now she wasn't so certain. Because if the Covenant had truly understood the extent of their own magnificent technology, they could have not only jumped into Slips.p.a.ceyrow a planet's atmosphere-but jumped into into a planet's atmosphere, too. a planet's atmosphere, too.

They could have simply bypa.s.sed Reach's...o...b..tal defenses.

The Covenant AI had called this heresy? Ludicrous.

Maybe the humans could eventually outthink the Covenant, given enough access to the enemy's technologies. Cortana realized the humans actually had a chance to win this war. All they needed was time.

"Cortana? Status please," the Master Chief said.

"Stand by," Cortana reported.

The Chief felt decompressive explosions reverberate through the deck, thunder that suddenly silenced itself as the atmosphere vented.

He waited for an explosion to tear through the engine room, or for plasma to envelop him. He scanned the engine room for any signs of Grunts or Elites, and then exhaled, and stared into the face of death for the countless time.

He had always been a hairsbreadth from death. John wasn't a fatalist, merely a realist. He didn't welcome the end; he knew, though, that he had done his best, fought and won so many times for his team, the Navy, and the human race . . . it made moments like this tolerable. They were, ironically, the most peaceful times in his life.

"Cortana, status please," he asked again.

There was a pause over the COM, then Cortana spoke. "We're safe. In Slips.p.a.ce. Heading unknown." She sighed, and her voice sounded tinged with weariness. "We're long gone from Halo, Threshold, and that Covenant fleet. If this tin can holds together a bit longer, I want to put some distance between us and them."