Becca hit the floor just as the last flash of sunlight vanished over the hills. Through her bedroom window, clouds were splashed across the darkening sky, soaking up the last drops of color from the departed sun. She could hear her mother humming as she moved about in the kitchen. A gentle bleating came from the goat pen in the backyard. A few papery leaves scraped across the dusty ground, rolling in the breeze, but Becca couldn't summon the strength to pull herself up to the window to see them.

Becca sat up and braced her back against the wall. A wave of nausea surged inside her, and she closed her eyes.

The changement had arrived.

The word itself was old, hundreds of years old, still tinged with the musty breath of French trappers who had intermarried with the Sioux and brought them this genetic gift. Changement was just their word for "change," but for the Sioux, it had come to mean so much more than that. It meant transformation. It meant "becoming."

Becca opened her mouth as her jaws suddenly stretched out in front of her and her teeth grew long, curved and gleaming white.

According to the legends of the French trappers, the changement was the transformation that turned some of their people into the long-limbed grey wolf - the loup-garou. The gift of transformation was so rare that it was mostly legend, but still the legend persisted. Among the Sioux, it explained the occasional howl heard in the night wind, across the prairie where wolves hadn't roamed for centuries.

Becca writhed silently on the floor, fighting the nausea. Her fingers folded in on each other and her nails surged out like black chips of broken asphalt. She shivered as thick gray hairs popped out of her skin and spread over her body. Suddenly, she felt a sharp tug inward, like a drawstring bag being pulled tight. She sighed. The changement was over.

It would come again the next morning and return her to human form, and the cycle would begin again, over and over, lasting until her period ended. At least for now, it was over. Becca lay quietly on the floor and wondered idly how it happened for boys. She resolved to ask one, if she ever found another loup-garou like herself.

Becca thought longingly of her older brother Charlie, whom their grandfather was now driving to the military base at Ellsworth. If she closed her eyes, she could almost hear the pickup truck rumbling in the distance. A thin whine escaped her throat. Charlie was really gone. He would go to Rapid City and in two days he would pass through the military gates at Ellsworth. And then? Someday, maybe, he would pass over Pine Ridge Reservation in one of his planes, like the eagle of Sioux legend who had saved a girl from the floodwaters drowning the earth. The girl had been carried to the tallest tree on the highest mountain in the Black Hills, where she became the eagle's wife and then mother to all of Charlie and Becca's people. But for Charlie, there was nothing here worth saving.

The phone call from the security guard had changed that. Becca felt a pang of guilt as she thought of her mother's voice, squeaking with disbelief over the phone as the guard relayed the charges. She'd been too far away to hear the exact words, and the guard wouldn't let her talk to her mother anyway, but the tone dripping with resignation was clear enough. Becca had swallowed bitterly then, and glared at the man in silence. She knew the charges weren't true. But would her mother believe her? Would Charlie? She had gripped the metal chair helplessly as the guard droned on, then dragged her feet to the car when a neighbor finally came to take her home.

Becca shook herself out of her reverie, then froze. Her ears pricked up. The noise in the kitchen had ceased.

"Becca?" Her mother's thin voice reached her through the door. "You okay, honey?"

Becca bolted upright on her haunches. She heard the clank of the pan as her mother set it down on the counter. Footsteps approached her door. Becca looked wildly around her room, then darted under the bed. She pressed herself against the back wall. The footsteps came closer, stopping right outside her door. "Becca?" her mother asked again. Becca held her breath. The door handle twitched, then started to turn.

The phone rang. Becca jumped. She flattened herself against the wall again. The door handle froze. The phone rang again, insistently. Becca saw the shadow under the door move away. She heard the footsteps retreating down the hallway. The receiver clicked. "Hello?" her mother said.

Becca breathed out slowly. She waited another minute, listening to the quiet murmur of conversation, then slipped out. She crawled up on the bed and looked out the window. A bright sliver of the full moon slipped under the now-purple hills and disappeared. The grass stretched before her, beautiful as the fringe of Wohlpe's dress that Becca's grandfather had told her about. He said once that the Earth was covered with the dress of a woman called Wohple who was loved by two brothers, the tempestuous North Wind and the gentle South Wind. The brothers soon realized they could not divide her between them, so they shared her. The North Wind frosted Wohlpe's dress with icy blizzards for half of the year, and the South Wind coaxed buffalograss and little bluestem from her fringe for the remainder. "Washtay," her grandfather concluded when the story was over. "It's harmonious. All things have their place in this cycle."

The changement had been coming for months now, but Becca had told no one. Not even Charlie. She didn't know how to explain the changes. She knew what they were, but she didn't understand what they meant. And it was getting harder to keep the secret now that she was having full transformations. At first it had just been night-roaming, where she wandered the fields half-asleep in human form, suddenly waking out in the hills with no memory of getting there. As the "becoming" grew stronger and more complete, she began to wander the lonely hills on her four grey paws, nose to the wind. Once, early on, when she was still in human form, Charlie had found her shivering on the open hills just behind their house. He had put his arm around her and guided her back home, half-grinning.

"Needed some fresh air, did you?" he'd asked. He'd held her close and ruffled her hair while she tried to shake off the sleepiness. She saw his questioning glance, but had known from his grin that he wouldn't believe her, so she'd shrugged and said it was just a case of sleepwalking.

Becca lay on her bed and breathed out, calmer. She needed Charlie. If she told him the truth about the security guard and the convenience store, he would understand. He wouldn't stay away forever. Maybe he could even help her understand the changement.

She had to go after him. She had to tell him the truth.

Becca sniffed the air and breathed in the faint traces of his musty scent. Through her bedroom window, she saw the first star appear in the ashy blackness. Becca stared across the dark prairie, then flew through the open window and loped off through the undulating grass.