Impulse.

Steven Gould.

ONE.

Millie: The Underlying Problem.

It was more of a lodge than a cabin but "cabin" is what they called it. The walls were made of heavy, thick logs, after all. The main living area was a broad space leaking from kitchen to dining area to a two-story-high lounge arranged around a tall, fieldstone fireplace.

Millie sat on one of the couches, staring out the windows, and frowned. It was snowing outside-big, fat, fluffy flakes-but she really wasn't noticing.

She was alone in the room and then she wasn't.

Davy was wearing a tropical-weight suit with the sleeves of the jacket rolled up on his forearms. He unrolled them as he asked, "What's wrong?"

Millie sighed, her eyes tracking up to the ceiling before returning to Davy's face.

Davy glanced up to the second-floor landing. "The usual?"

Millie jerked her thumb up. "Go look at her door."

He sighed. "She is an irritation of the spirit...."

Millie completed the phrase, "... and a great deal of trouble."

Davy vanished. After a brief pause Millie heard laughter drift down the staircase. Millie stood and jumped, appearing beside Davy in the upstairs hallway.

A sign, scrawled on butcher paper, was tacked to a closed bedroom door. It said: HELP!.

BEING HELD PRISONER BY TELEPORTING ALIENS!.

KEPT FROM NORMAL LIFE.

SEND FRIENDS.

ALSO ICE CREAM.

Davy was shaking his head and still laughing.

"Stop it!" Millie said. "You're not helping!"

"You gotta admit, she is funny," Davy said. "Takes after me that way."

Millie snapped. "What-you think you're funny?" She pulled at Davy's arm, leading him back toward the landing.

Davy raised his eyebrows at Millie and grinned.

"Okay, she is funny, but the underlying problem is no less a problem."

Davy's smile faded and he jerked his chin down toward the kitchen, and vanished.

Millie followed to see him putting the kettle on.

"What choice do we have?" Davy said. "I mean, really?"

Millie shook her head. She felt like she should have an answer but she didn't.

Davy hugged her and that was good ... but the underlying problem was still no less a problem.

And it could only get worse.

TWO.

Cent: "But it will kill you dead, just the same."

I don't really exist, you know.

We live in the Canadian Rockies, sixty miles south of the Arctic Circle. I was born here, in this house. Mom and Dad paid a nurse midwife to live with us for the last month of the pregnancy. Dad was prepared to transfer Mom to a hospital if things went wrong, but things "worked out" as did I, apparently. Mom said it was definitely "work."

But there's no birth record. No birth certificate. No Social Security number.

We're in the middle of nowhere. The second largest city in the province is a hundred miles to the southeast, but I've never been there. Next nearest town is 140 miles north: Old Crow. No roads to Old Crow, it just has an airstrip and the river.

No roads to our house, either. It was built by a billionaire as a hunting lodge at the head of a mountain valley using helicoptered labor. We get moose, caribou, deer, wolves, lynx, and rabbits. Starbucks? Not so much.

The walls are heavy logs, two feet thick. The roof is steeply pitched anodized steel to keep the snow from piling up. It sloughs off the snow in the winter until the bottom floor windows and doors are buried. One year the snow rose high enough to cover the second floor, but Dad melted it away, making sure that the chimney, ventilation stacks, upper doors, and triple-glazed windows remained clear.

There's a log-surfaced helicopter pad, but Dad does nothing to keep it clear, no matter what the season. Moss, brush, and small trees are taking it over.

Dad doesn't care. That's not how he rolls.

He does spend a lot of the summers fixing up the lodge itself-that and the springhouse out back.

The springs are the reason the billionaire built the lodge here: one hot, one cold. One tasting of sulfur and one tasting like a deep breath of winter. We don't need a hot-water heater-the hot spring provides bath, washing, and soaking water-though it leaves mineral stains in the tub. We drink from the cold spring and use it to make showers less scalding. For two thirds of the year we run hot spring water through radiators to heat the house, and all year round we use the temperature difference between the two springs to generate electricity.

That was Dad's doing. I think back when it was a hunting lodge, they had a diesel generator. But it was rusted solid when Dad bought the place. The billionaire had become a mere millionaire during the economic meltdown and a vacation home that required two-hundred-mile round-trips by helicopter became something he couldn't afford.

Dad's not a billionaire, but then he doesn't need a helicopter to get here, either.

The electrical generator came from an Icelandic power company that built it as a proof-of-concept device at one of their geothermal wells. When they upgraded that installation to the megawatt commercial version, Dad bought the prototype for mere thousands of dollars.

When I was little, I named it Buzz since that's what it does, sits in the basement and buzzes. To be fair, it also gurgles, hisses, and thumps, but for a four-year-old, buzz is as entertaining a word as ever there was, especially if you add extra "zzzzzzzzzzzz" at the end.

And then one day, when I was fifteen, it stopped buzzing.

I was watching an old anime on my desktop, but the screen blipped out along with the lights and then I was sitting in the dark, listening to the DVD drive spin to a halt.

I heard Mom yell from her office across the hall. "Davy!"

Dad's voice answered from downstairs, "Yeah, yeah. I'm on it!"

I felt my way over to the door and opened it. The battery-powered emergency light in the stairwell had come on. The windows were dark-it was late afternoon and October, and what little dusk light was on the southern horizon was blocked by the ridge on the far side of the valley.

Dad had just come out of the library when I tripped down the stairs. He smiled briefly at me. "Hey, Cent. Pretty dark up there, I bet."

"You think?" I said. "What's wrong with Buzz?"

He shook his head. "Not sure. Let's go see." He reached out to ruffle my hair.

I was styling it these days with a lot of gel and I slapped his arm away. "Rule one, Daddy! How many times do I gotta tell you?"

He laughed again. "Don't touch the hair. Right. Sorry."

I swear he does it just to mess with me.

When he opened the door at the top of the basement stairs, I heard a high-pitched beeping noise, one I'd never heard before. I started to take a step down and Dad grabbed me by my collar and pulled me back.

"Damn!" Dad said. "Well, at least we know what's wrong with Buzz. Don't go down there."

"What's that alarm?"

"Halogen detector. There's a leak in the system. The Freon is leaking out." He was no longer smiling.

I knew about the Freon. The hot water from the spring boils it to vapor, which expands through the turbine generator. The cold spring water condenses it again. I'm homeschooled, so the generator has been the source of many science lessons: state changes of matter, Boyle's law, electromagnetism.

"Freon isn't poisonous, Dad."

"No. But it will kill you dead, just the same." The serious look on his face eased at my expression. "Definitely not poisonous. We're okay up here. Let me give you a clue: Freon is heavier than air."

I thought about it for a moment. "Ah. Like water?"

"Like water you can't see or feel or smell, yes. Which means?"

"The air is on top. The Freon fills up the basement and pushes the air out."

He grinned, big. "On the nosey, little posy."

"You'd pass out, eh?"

"Before you died. Heard about a shrimp boat with a refrigeration leak down in the hull. Different members of the crew kept going down into the hold to see what happened to the previous guy. The coast guard found the vessel going in circles, everybody suffocated."

I eyed the stairs dubiously. "You sure we're okay?"

He got that look on his face and smiled.

"No!" I said. "I don't need another real-life math problem!"

He led me back upstairs where we found Mom typing at her computer. She had a laptop with a battery. She didn't have to stop what she was doing because Buzz was busted.

"What's wrong with Buzz?" she asked.

"Leaking Freon," Dad said calmly.

"And displacing all the air in the house!" I said.

Mom's eyes widened and she looked at Dad. Dad shrugged. "Not very likely, but Millicent is going to calculate the answer to that."

Mom raised her eyebrows and pushed a pad of paper and a pen toward me across her desk.

Dad said, "Assume an eight-foot-high ceiling. The generator room is twelve by ten feet. It's about a quarter of the entire basement."

I did that part in my head. "Nine-hundred-sixty cubic feet. How much Freon?"

Dad jumped and I don't mean he bounced in place. He disappeared, vanished. I said something under my breath, which caused Mom to sit up straight and give me "the look."

"Sorry. I was watching my show. I already did homework today." I sounded whiny. I hate sounding whiny. I tried again, with a more reasonable voice. "I work hard, don't I?"

"The look" faded and Mom said, "Yes, honey, you do. But you know your father. He never finished school. He's one of the smartest men I know but he has this thing about education."

"Tell me about it. If I hear the phrase 'teachable moment' one more time, I'm gonna barf."

Dad reappeared at my elbow, a manual and a sheet of paper in his hand. "Had to go to the library for the Material Safety Data sheet. Didn't know the density."

I looked at Mom and sighed heavily. Dad put the books on the desk by the notepad and slid a chair over for me to sit.

It was dark, but when he pulled the bedroom door all the way open, the emergency light from the hall shone across half the desk.

"Dad! This is Buzz's manual-you went into the basement!"

He shrugged. "As you said, it's not poisonous. I held my breath. Wasn't in there more than five seconds." Mom and I both gave him "the look" but after so many years, he's impervious. He reached down and tapped the notepad.

I sighed and sat down. The manual specs said the generator was charged with 175 pounds of Freon, the ozone-safe R-22 version. The Material Data Sheet told me the density, and when I converted, I got .225 pounds per cubic foot. That seemed pretty heavy but I double-checked it. "Must be a big molecule." I grabbed Mom's laptop and called up a calculator. "Seven hundred and eighty cubic feet. Uh, in the generator room that would displace the air up to, uh, six and a half feet off the floor."

Dad held his hand over his head. "Worse than that, I think. You didn't account for altitude."

"Oh." I blushed. As I'd said, we'd already done Boyle's law but I'd forgotten. I knew the conversion factor for our forty-five hundred feet of altitude by heart. "Okay." I multiplied the figure by 1.18. "Call it 920 cubic feet." I tapped away. "It would fill the room to seven and two-thirds feet."