Prologue

Dog lay curled up on the concrete floor of the helicopter hangar, a metallic, high-pitched whine escaping him. He should never have left his pack.

There had been a large blue storm in the sky made out of clouds, like a giant upside-down pool of water pouring out of the Citadel. Dog wasn't too sure what it was, but it was giving off strange signals all along the light spectrum, and everyone seemed worried about it until they launched that rocket. The rocket flew up, up, up... until it disappeared behind the clouds. With a flash of light that vibrated the ground even from their distance, the bluish bands of vapor faded out of existence.

Master, Alyx, and Gordon burst into cheers. Alyx turned and said, "We did it, Gordon!"

Dog didn't know what all the jubilee was about, but he was content to sit back and be happy his pack was happy; even the new member, the orange man named Gordon, whom Alyx seemed to be so fond of. For the first time since those interlopers on three legs had torn his territory apart, Dog felt safe.

But... no, something was off. Some sort of signal flashed from deep in the trees. Curious, he cocked his head toward the forest.

What is that? he thought. The signal was like a sound, but - not. It happened again.

What IS that? It was like a flash, but not. He looked at his pack to see if they had noticed. They were still smiling and talking; Master and Alyx hugged, and spoke to Gordon, who looked tired, so tired, but peaceful.

"I'll bet the Combine aren't too happy right now!" she boasted.

Master leaned heavily on his false leg. "You got that right, sweetheart, but we've got plenty to celebrate. I wish you didn't have to head off so soon..."

They hadn't even noticed. As they kept speaking, Dog resolved to investigate the signal from the woods. It was like a beacon, riding on a frequency their ears couldn't hear, their eyes couldn't see, calling him through the trees.

It must be an intruder, he decided. An intruder, he thought indignantly, in MY territory! He clambered over the fence after the beacon, after the intruder. Behind him, he heard Alyx say, "Dog? Hey, where are you -" but he kept running. Her shrinking voice said, "What a nut. Don't go too far!"

It was a strange sound, yet oddly familiar, like something he occasionally heard hovering behind the white noise on an abandoned radio frequency. It was mechanical, like him, but also alien, like his vort friends. As he ran through the trees its source eluded him, weaving oddly through the forest unlike a vehicle, unlike an animal.

As he ran farther and farther from the base, he grew uncertain. But he was getting close, he was getting so close to catching the - the thing on his territory. Just when he was about to turn back, he came upon a small meadow and stopped in his tracks. Dominating the clearing was a... what was that? A huge, white bean in a metal case? With a snout? He scrutinized it with more curiosity than fear. It hovered a few feet off the ground. Well, it was definitely the source of the signal.

No sooner did he think that than the beacon suddenly switched off and the creature made an abrupt mechanic whine of smug victory and shot straight up into the air. Dog craned his neck to follow its flight; ha, funny, it almost seemed to be heading toward base...

Dog's iris twitched. Oh, no. It was moving so quickly, straight the way he had just come. Oh no oh no oh no oh no oh no! He ran so fast his feet dug little holes into the earth and the surrounding greenery was a cold blur.

He could hear them before he could see the hangar. There were voices, screams!

Master's strangely calm voice said, "I love you, sweetheart. Close your eyes, honey!"

Alyx yelled, "I love you, Dad!"

"Don't look -" but his words were cut short by a horrible crunching, squelching sound and Alyx screaming, "No! Oh my God, no!"

He counted down the meters to the base until finally, finally, finally, the hangar came into view. Dog leapt up the wall and stuck his head through a hole in the roof. It took him a moment to digest what he saw: Gordon was pinned against a wall by an unnatural force, his face tortured. There were two of the strange creatures! One was holding Master by the neck, but he was so still, so terribly still, and the other was slowly dragging Alyx toward it. She was weeping, struggling weakly, her face twisted with despair. She managed to half-turn her head and cry, "Gordon," but stopped when her eyes locked on the hole in the roof. "Dog!"

Dog jumped. He plowed his iron fist through the metal casing of the creature holding Alyx over and over until it dropped her, its companion dropped Master, and they retreated through the ceiling. After that, the only thing he could do was stand there and watch as she cradled Master.

Shame. Shame overwhelmed him until all he wanted to do was curl up in a corner, bury his head, and never move from that spot.

Master was dead, and he was a very bad dog.