"No. Cortana resides in the interface between your mind and the suit, Master Chief. You will find your reaction time greatly improved. She will be translating the impulses in your motor cortex directly into motion-she can't make you send those impulses."

"This AI," he said, "will beinside my mind?" That must have been what that "upgrade" to his standard- issue UNSC computer interface had been for. "That is the question, isn't it?" Halsey replied. "I can't answer that, Master Chief. Not scientifically." "I'm not sure I understand, Doctor." "What is the mind, really? Intuition, reason, emotion-we acknowledge they exist, but we still don't my mind?" That must have been what that "upgrade" to his standard- issue UNSC computer interface had been for. "That is the question, isn't it?" Halsey replied. "I can't answer that, Master Chief. Not scientifically." "I'm not sure I understand, Doctor." "What is the mind, really? Intuition, reason, emotion-we acknowledge they exist, but we still don't know what makes the human mindwork ." She paused, searching for the right words. "We model AIs on human neural networks-on electrical signals in the brain-because we just know that the human brain works . . . but not how, or why. Cortana resides 'between' your mind and the suit, interpreting the electrochemical messages in your brain and transferring them to the suit via your neural implant. ." She paused, searching for the right words. "We model AIs on human neural networks-on electrical signals in the brain-because we just know that the human brain works . . . but not how, or why. Cortana resides 'between' your mind and the suit, interpreting the electrochemical messages in your brain and transferring them to the suit via your neural implant.

"So, for lack of a better term, yes, Cortana will be 'inside' your mind."

"Ma'am, my priority will be to complete this mission. This AI-Cortana-may have conflicting directives."

"There is no need to worry, Master Chief. Cortana has the same mission parameters as you do. She will do anything necessary to make sure that your mission is accomplished. Even if that means sacrificing herself-or you-to accomplish it."

The Master Chief exhaled, relieved.

"Now, please kneel down. It's time to insert her memory-processor matrix into the socket at the base of your neck."

The Master Chief knelt. There was a hissing noise, a pop, and then cold liquid poured into the Master Chief's mind; a spike of pain jammed into his forehead, then faded.

"Not a lot of room in here," a smooth female voice said. "h.e.l.lo, Master Chief."

Did this AI have a rank? Certainly, she was not a civilian-or a fellow soldier. Should he treat her like any other piece of UNSC-issued equipment? Then again, he treated his equipment with the respect it deserved. He made sure every gun and knife was cleaned and inspected after every mission.

It was unsettling . . . he could hear Cortana's voice through his helmet speakers, but it also felt like she was speaking inside his head. "h.e.l.lo, Cortana."

"Hmm . . . I'm detecting a high degree of cerebral cortex activity. You're not the muscle-bound automatons the press makes you out to be."

"Automaton?" the Master Chief whispered. "Interesting choice of words for an artificial intelligence."

Dr. Halsey watched the Master Chief with great interest. "You must forgive Cortana, Master Chief. She is somewhat high-spirited. You may have to allow for behavioral quirks."

"Yes, ma'am."

"I think we should begin the test straightaway. There's no better way for the two of you to get acquainted than in simulated combat."

"No one said anything about combat," Cortana said. "The ONI bra.s.s have arranged a test for you and the new MJOLNIR system," Dr. Halsey said. "There are some that believe you two are not up to our proposed mission."

"Ma'am!" The Master Chief snapped to attention. "I'm up for it, ma'am!" "I know you are, Master Chief. Others . . . require proof." She looked around at the shadows cast by the Marines outside the fabric walls of the command dome. "You hardly need a reminder to be prepared for anything . . . but stay on your guard, just the same." Dr. Halsey's voice dropped to a whisper. "I think some of the ONI bra.s.s would prefer to see you fail this test, Master Chief. And they may have arranged to make sure you do-regardless of your performance." "I won't fail, Doctor." Her forehead wrinkled with worry lines, but then they quickly disappeared. "I know you won't." She stepped back, and dropped her conspiratorial whisper. "Master Chief, you are ordered to count to ten after I leave. After that, make your way to the obstacle course. At the far end is a bell. Your goal will be to ring it." She paused, then added, "You are authorized to neutralize any threats in order to achieve this objective."

"Affirmative," the Master Chief said. Enough uncertainty-now he had an objective, and rules of engagement. "Be careful, Master Chief," Dr. Halsey said quietly. She gestured at the pair of technicians to follow her, then turned and walked out of the tent.

The Master Chief didn't understand why Dr. Halsey thought he was in real danger-he didn't have to understand the reason. All he needed to know was that danger was present.

He knew how to handle danger. "Uploading combat protocols now," Cortana said. "Initiating electronic detection algorithms. Boosting neural interface performance to eighty-five percent. I'm ready when you are, Master Chief."

The Master Chief heard metallic clacks around the tent.

"a.n.a.lyzing sound pattern," Cortana said. "Database match.Identified as-"

"As someone cycling the bolt of an MA5B a.s.sault rifle. I know. Standard-issue weapons for Orbital Drop Shock Troopers." "Since you're 'in the know,' Master Chief," Cortana quipped. "I a.s.sume you have a plan." John snapped his helmet visor back down and sealed the armor's environment system. "Yes." "Presumably your plan doesn't involve getting shot . . . ?" "No." "So, what's the plan?" Cortana sounded worried. "I'm going to finish counting to ten." John heard Cortana sigh in frustration. John shook his head in puzzlement. He'd never encountered a so- called smart AI before. Cortana sounded . . . like a human. Worse, she sounded like acivilian . This was going to take a lot of getting used to. Shadows moved along the wall of the tent-motion from outside. . This was going to take a lot of getting used to. Shadows moved along the wall of the tent-motion from outside.

Eight.

There was a snag in this mission and he hadn't even reached the obstacle course. He would have to engage his fellow soldiers. He pushed aside any questions about why. He had his orders and he would follow them. He had dealt with ODSTs before.

Nine.

Three soldiers entered the tent, moving in slow motion-black-armored figures, helmets snug over their faces, crouched low, and their rifles leveled. Two took flanking positions. The one in the middle opened fire.

Ten.

The Master Chief blurred into motion. He dove from the activation platform and-before the soldiers could adjust their aim-landed in their midst. He rolled to his feet right next to the soldier who fired first, and grabbed the man's rifle.

John brutally yanked the weapon away from the soldier. There was a loud cracking sound as the man's shoulder dislocated. The wounded trooper stumbled forward, off balance. John spun the rifle and slammed the b.u.t.t of the weapon into the soldier's side. The man exhaled explosively as his ribs cracked. He grunted, and fell unceremoniously to the floor, unconscious.

John spun to face the left-flank gunner, a.s.sault rifle leveled at the man's head instantly. He had the man in his sights, but he still had time-the soldier was not quite in position. To John's enhanced senses, amped up by Cortana and the neural interface, the rifleman seemed to be moving in slow motion. Too slow.

The Master Chief lashed out with the rifle b.u.t.t again. The trooper's head snapped back from the sudden, powerful blow. He flipped head over tail and slammed into the ground. John sized the man's condition up with a practiced eye: shock, concussion, fractured vertebrae.

Gunner number two was out of the fight.

The remaining gunner completed his turn and opened fire. A three-round burst ricocheted off the MJOLNIR armor's energy shield. The shield's recharge bar flickered a hairbreadth.

Before the soldier could react, the Master Chief sidestepped and slammed his own rifle down-hard. The trooper screamed as his leg gave out. A jagged spoke of bone burst through the wounded man's fatigues. The Master chief finished him with a rifle b.u.t.t to his helmeted head.

John checked the condition of the rifle, and-satisfied that it was in working order-began to pull ammo clips from the fallen soldiers' belt pouches. The lead soldier also carried a razor-edged combat knife; John grabbed it.

"You could have killed them," Cortana said. "Why didn't you?"

"My orders gave me permission to 'neutralize' threats," he replied. "They aren't threats anymore."

"Semantics," Cortana replied. She sounded amused. "I can't argue with the results, though-" She broke off, suddenly. "New targets. Seven contacts on the motion tracker," Cortana reported. "We're surrounded."

Seven more soldiers. The Master Chief could open fire now and kill them all. Under any other circ.u.mstances, he would have removed such threats. But their MA5Bs were no immediate danger to him . . . and the UNSC could use every soldier to fight the Covenant.

He strode to the center pole of the tent, and with a yank, he pulled it free. As the roof fluttered down, he slashed a slit in the tent fabric and shoved through. He faced three Marines; they fired-the Master Chief deftly jumped to one side. He sprang toward them and lashed out with the steel pole, swiped out their legs. He heard bones crack-followed by screams of pain. The Master Chief turned as the tent finished collapsing. The remaining four men could see him now.

One reached for a grenade on his belt. The other three tracked him with their a.s.sault rifles.

The Master Chief threw the pole like a javelin at the man with the grenade. It impacted in his sternum and he fell with awhoopf. The grenade, minus the pin, however, dropped to the ground. The Master Chief moved and kicked the grenade. It arced over the parking lot and detonated in a cloud The grenade, minus the pin, however, dropped to the ground. The Master Chief moved and kicked the grenade. It arced over the parking lot and detonated in a cloud of smoke and shrapnel.

The three remaining Marines opened fire-spraying bullets in a full-auto fusillade. Bullets pinged off the Master Chief's shield. The shield status indicator blinked and dropped with each bullet impact-the sustained weapons fire was draining the shield precipitously. John tucked and rolled, narrowly avoiding an incoming burst of automatic-weapons fire, then sprang at the nearest Marine. John launched an openhanded strike at the man's chest. The Marine's ribs caved in and he dropped without a sound, blood flowing from his mouth. John spun, brought his rifle up, and fired twice.

The second soldier screamed and dropped his rifle as the bullets tore through each knee. John kicked the discarded rifle, bending the barrel and rendering the weapon useless.

The last man stood frozen in place. The Master Chief didn't give the man time to recover; he grabbed his rifle, ripped off his bandolier of grenades, then punched his helmet. The Marine dropped.

"Mission time plus twenty-two seconds," Cortana remarked. "Although, technically, you started to move forty milliseconds before you were ordered to." "I'll keep that in mind." The Master Chief slung the a.s.sault rifle and bandolier of grenades over his shoulder and ran for the shadows of the barracks. He slipped under the raised buildings and belly-crawled toward the obstacle course. No need to make himself a target for snipers . . . although it would be an interesting test to see what caliber of bullet these shields could deflect.

No. That kind of thinking was dangerous. The shield was useful, but under combined fire it dropped very quickly. He was tough . . . not invincible.

He emerged at the beginning to the obstacle course. The first part was a run over ten acres of jagged gravel. Sometimes raw recruits had to take off their boots before they crossed. Other than the pain-it was the easiest part of the course.

The Master Chief started toward the gravel yard.

"Wait," Cortana said. "I'm picking up far infrared signals on your thermal sensors. An encrypted sequence . . . decoding . . . yes, there. It's an activation signal for a Lotus mine. They've mined the field, Master Chief."

The Master Chief froze. He'd used Lotus mines before and knew the damage they could inflict. The shaped charges ripped though the armor plate of a tank like it was no thicker than an orange peel.

This would slow him down considerably.

Not crossing the obstacle course was no option. He had his orders. He wouldn't cheat and go around. He had to prove that he and Cortana were up for this test.

"Any ideas?" he asked.

"I thought you'd never ask," Cortana replied. "Find the position of one mine, and I can estimate the rough position of the others based on the standard randomization procedure used by UNSC engineers."

"Understood."

The Master Chief grabbed a grenade, pulled the pin, counted to three, and lobbed it into the middle of the field. It bounced and exploded-sending a shock wave through the ground-tripping two of the Lotus mines. Twin plumes of gravel and dust shot into the air. The detonation shook his teeth.

He wondered if the armor's shields could have survived that. He didn't want to find out while he was still inside the thing. He boosted the field strength on the bottom of his boots to full.

Cortana overlaid a grid on his heads-up display. Lines flickered as she ran through the possible permutations.

"Got a match!" she said. Two dozen red circles appeared on his display. "That's ninety-three percent accurate. The best I can do."

"There are never any guarantees," the Master Chief replied. He stepped onto the gravel, taking short, deliberate steps. With the shields activated on the bottoms of his boots, it felt like he was skating on greased ice.

He kept his head down, picking his way between red dots on his display. If Cortana was wrong, he probably wouldn't even know it. The Master Chief saw the gravel had ended. He looked up. He had made it. "Thank you, Cortana. Well done." "You're welcome . . ." Her voice trailed off. "Picking up scrambled radio frequencies on the D band.

Encrypted orders from this facility to Fairchild Airfield. They're using personal codewords, too-so I can't tell what they're up to. Whatever it is, I don't like it." "Keep your ears open."

"I always do." He ran to the next section of the obstacle course: the razor field. Here, recruits had to crawl in the mud under razor wire as their instructors fired live rounds over them. A lot of soldiers discovered whether they had the guts to deal with bullets zinging a centimeter over their heads.

Along either side of the course there was something new: three 30mm chain-guns mounted on tripods. "Weapons emplacements are targeting us, Chief!" Cortana announced. The Master Chief wasn't about to wait and see if those chain-guns had a minimum-depth setting. He had no intention of crawling across the field and letting the chain-guns' rapid rate of fire chip away at his shields.

The chain-guns clicked and started to turn. He sprinted to the nearest tripod-mounted gun. He opened fire with his a.s.sault fire, shot the lines that powered the servos-then spun the chain-gun around to face the others.

He crouched behind the blast shield and unloaded on the adjacent gun. Chain-guns were notoriously hard to aim; they were best known for their ability to fill the air with gunfire. Cortana adjusted his targeting reticle to sync up with the chain-gun. With her help, he hit the adjacent weapon emplacements. John guided a stream of fire into the guns' ammo packs. Moments later, in a cloud of fire and smoke, the guns fell silent . . . then toppled.

The Master Chief ducked, primed a grenade, and hurled it at the closest of the remaining automated weapons. The grenade sailed through the air-then detonated just above the autogun.

"Chain-gun destroyed," Cortana reported. Two more grenades and the automated guns were out of commission. He noted that his shields had dropped by a quarter. He watched the status bar refill. He hadn't even known he had taken hits. That was sloppy.

"You seem to have the situation under control," Cortana said, "I'm going to spend a few cycles and check something out." "Permission granted," he said. "I didn't ask, Master Chief," she replied. The cool liquid presence in his mind withdrew. The Master Chief felt empty somehow. He ran through the razor fields, snapping through steel wire as if it were rotten string.

Cortana's coolness once again flooded his thoughts. "I just accessed SATCOM," she said. "I'm using one of their satellites so I can get a better look at what's happening down here. There's a SkyHawk jump jet from Fairchild Field inbound."

He stopped. The automatic cannons were one thing-could the armor withstand against air power like that? The SkyHawk had a quartet of 50mm cannons that made the chain-guns look like peashooters. They also had Scorpion missiles-designed to take out tanks.

Answer: he couldn't do a thing against it.

The Master Chief ran. He had to find cover. He sprinted to the next section of the course: the Pillars of Loki. It was a forest of ten-meter-tall poles s.p.a.ced at random intervals. Typically, the poles had b.o.o.by traps strung on, under, and between them-stun grades, sharpened sticks . . . anything the instructors could dream up. The idea was to teach recruits to move slowly and keep their eyes open.

The Master Chief had no time to search for the traps. He climbed up the first pole and balanced on top. He leaped to the next pole, teetered, regained his balance-then jumped to the next. His reflexes had to be perfect; he was landing a half ton of man and armor on a wooden pole ten centimeters in diameter.

"Motion tracking is picking up an incoming target at extreme range," Cortana warned. "Velocity profile matches the SkyHawk, Chief." He turned-almost lost his balance and had to shift back and forth to keep from falling. There was a dot on the horizon, and the faint rumble of thunder.

In the blink of an eye, the dot had wings and the Master Chief's thermal sensors picked up a plume of jetwash. In seconds, the SkyHawk closed-then opened fire with its 50mm cannons. He jumped.

The wooden poles splintered into pulp. They were mowed down like so many blades of gra.s.s. The Master Chief rolled, ducked, and flattened himself on the earth. He caught a smattering of rounds and his shield bar drooped to half. Those rounds would have penetrated his old suit instantly.

Cortana said, "I calculate we have eleven seconds before the SkyHawk can execute a maximum gee turn and make another pa.s.s." The Master Chief got up and ran through the shattered remains of the poles. Napalm and sonic grenades popped around him, but he moved so fast he left the worst of the damage in his wake.

"They won't use their cannons next time," he said. "They didn't take us out-they'll try the missiles." "Perhaps," Cortana suggested, "we should leave the course. Find better cover." "No," he said. "We're going to win . . . by their rules." The last leg of the course was a sprint across an open field. In the distance, the Master Chief saw the bell on a tripod. He glanced over his shoulder.

The SkyHawk was back and starting its run straight toward him.

Even with his augmented speed, even with the MJOLNIR armor-he'd never make it to the bell in time. He'd never make it alive. He turned to face the incoming jet. "I'll need your help, Cortana," he said. "Anything," she whispered. The Master Chief heard nervousness in the AI's voice. "Calculate the inbound velocity of a Scorpion missile. Factor in my reaction time and the jet's inbound speed and distance at launch, and tell me the instant I need to move to sidestep and deflect it with my left arm."

Cortana paused a heartbeat. "Calculation done. You did say 'deflect'?" "Scorpion missiles have motion-tracking sensors and proximity detonators. I can't outrun it. And it won't miss. That leaves us very few options."

The SkyHawk dove. "Get ready," Cortana said. "I hope you know what you're doing." "Me, too." Smoke appeared from the jet's left wingtip and fire and exhaust erupted as a missile streaked toward him. The Master Chief saw the missile's track back and forth, zeroing in on his coordinates. A shrill tone in his helmet warbled-the missile had a guidance lock on him. He chinned a control and the sound died out. The missile was fast. Faster than he was ten times over.

"Now!" Cortana said. They moved together. He shifted his muscles and the MJOLNIR-augmented by his link to Cortana- moved faster than he'd ever moved before. His leg tensed and pushed him aside; his left arm came up and crossed his chest.

The head of the missile was the only thing he saw. The air grew still and thickened.

He continued to move his hand, palm open in a slapping motion-as fast as he could will his flesh to accelerate. The tip of the Scorpion missile pa.s.sed a centimeter from his head. He reached out-fingertips brushed the metal casing- -and slapped it aside. The SkyHawk jet screamed over his head.

The Scorpion missile detonated. Pressure slammed though his body. The Master Chief flew six meters, spinning end over end, and landed flat on his back.

He blinked, and saw nothing but blackness. Was he dead? Had he lost?

The shield status bar in his heads-up display pulsed weakly. It was completely drained-then it blinked red and slowly started to refill. Blood was spattered across the inside of his helmet and he tasted copper. He stood, his muscles screaming in protest. "Run!" Cortana said. "Before they come back for a look." The Master Chief got up and ran. As he pa.s.sed the spot where he had stood to face down the missile, he saw a two-meter-deep crater.

He could feel his Achilles tendon tear, but he didn't slow. He crossed the half-kilometer stretch in seventeen seconds flat and skidded to halt. The Master Chief grabbed the bell's cord and rang it three times. The pure tone was the most glorious sound he had ever heard. Over the COM channel Dr. Halsey's voice broke:"Test concluded. Call off your men, Colonel Ackerson! We've won. Well done, Master Chief. Magnificent! Stay there; I'm sending out a recovery team."

"Yes, ma'am," he replied, panting.

The Master Chief scanned the sky for the SkyHawk-nothing. It had gone. He knelt and let blood drip from his nose and mouth. He looked down at the bell-and laughed.

He knew that stainless-steel dented shape. It was the same one he had rung that first day of boot. The day Chief Mendez had taught him about teamwork.

"Thank you, Cortana," he finally said. "I couldn't have done it without you."

"You're welcome, Master Chief," she replied. Then, her voice full of mischief, she added: "And no, you couldn't have done it without me."

Today he had learned about a new kind of teamwork with Cortana. Dr. Halsey had given him a great gift. She had given him a weapon with which to destroy the Covenant.