She studied her target. He was seated and had fallen asleep on the job. Awake or asleep, he'd never know what hit him. He had an AK balanced across his knees, his head lowered. Her angle was perfect so that the round would not penetrate the house after traversing his skull.

Diaz had considered the wind speed and direction, automatically displayed in her HUD. She had her range, which was decreased by the specially modified 7.62 mm subsonic ammunition she fired to dampen her rifle's report. She'd already accounted for the force of gravity, the bullet drop.

This was the math every good sniper knew, not unlike the math they'd tried to sell you in high school: "Hey, kids, if you ever become an Army Special Forces sniper, you'll need this stuff." Perhaps they would have had more luck gaining students' attention if they had framed it like that.

And this was the math that had cost Diaz most of her romantic relationships with men. She could never tell them what she actually did in the army, and the lies never added up.

Besides, what man in his right mind would want a crazy woman like her, who would kite off on a whim to Europe to learn foreign languages when she wasn't shooting bad guys? Most of the men she had dated wanted a woman who was into pizza, beer, and sports, not a woman who watched PBS on TV.

But this was the math. And all of her calculations were, at the moment, complete.

Her reticle floated over the target and froze. Perfect head shot.

Her trigger finger came down slowly, gracefully, followed by a muted thump and puff of smoke.

The round struck the guard's head, took most of it off, and left him slumping sideways. No piece of him had struck the door. Even Diaz couldn't believe she'd killed him so cleanly.

"Nice," said the captain. "That's one."

"Stand by," she said, hearing the voices of her brothers like she always did when trying to take aim:

"Come on, girly girl, shoot it! Bet you'll miss!"

I don't think so, Carlos.

"She ain't going to hit it."

Watch me, Tomas. Just watch me.

The second guard had stirred and was now looking up. Diaz didn't have much time. She checked the readings in her HUD, adjusted her aim, and found the guard's head.

Her brothers were screaming now.

And the round cut loose from her rifle.

The guard joined his comrade, spilling blood onto the snow, dying silently.

"Last one," said the captain.

"I have him," answered Diaz.

"Brown, Ramirez, stand by to move," warned the captain.

"She ain't getting this one," said Carlos.

"Maybe," said Tomas. "She ain't missed one yet!"

A gust of wind ripped over the mountain, blowing snow across Diaz's field of view. She cursed and readjusted her position.