Now, when I see teenage girls laughing. When I see them loosed on a summer evening -- their limbs tanned and gossamer, their imagined freedom radiating like nuclear light -- I can't help but fast-forward two decades or more. I know the curve of their bones has already made an imperceptible bow to gravity. I see the decay in slow motion, even or especially through those stunning and immortal years.

But Skye could see it then. At seventeen, she spoke about her childhood with the most yearning nostalgia, like an old woman looking back at youth.

"I used to swim past Tautog Rock in October," she told me, sitting in the open window of my dorm room. "I used to ride my bike down Scargo Hill without ever touching the brakes."

She threw out her arms -- so freckled and slender, they might still have belonged to that ten-year-old, tearing around Cape Cod.

I sat on the floor, cutting lines of Columbian cocaine on top of my toaster oven. With the flourish of a Japanese chef, I used a razor blade to fan, dice, and separate. The coke was fine and completely pure. It coursed through our bodies with none of the usual side effects: no gas or worried jaws. Only wide open lucidity, exhilaration, confidence.

"Fearless," Skye said, pronouncing the word with greed, as if the quality had long since left her, and she would spend the rest of her life chasing it down.

The autumn air hung behind her in complete darkness. If headmasters were smart, they would employ floodlights -- no shadows anywhere, to slip between. But at the Esther Percy School for Girls, we saw not a glint of orange or red from outside, just heard the wind soughing through brilliant leaves.

"But it's okay," Skye said. "Nobody stays young forever, right?"

I laughed. "I don't think you're ready for dentures just yet."

She stretched in the dimly watted light. The strap of my white eyelet nightgown -- bought by my mother in Paris -- slid off her shoulder.

"At our Cape house," she said, "we've got powder post beetles in the beams. You can hear them at night, gnawing away like little buzz saws. Sometimes I think I hear them in my bones. Chzz chzz chzz."

I lifted the toaster oven toward Skye, and she collected her long, red curls. With a plastic straw, stolen from the dining hall and snipped in half, she inhaled a line. Before tonight, Skye had never done cocaine -- or any drug, other than sips from her father's wineglass. But she wielded the accouterments with surprising grace. When the line vanished, she sat up and ran one finger across the bridge of her nose -- her face smooth and white as a teacup.

She sniffed and shivered, then asked me if I believed in an afterlife.

"Sure," I said.

What I really believed in was this life, continuing on indefinitely. Sweet, acrid powder melted and dripped down the back of my throat. I blinked like an animal -- completely and deliciously awake. What we lacked was a fire to dance around. Deer to chase down and slay. Instead of this small wooden room and the most simplistic metaphysics.

"Me too," Skye said. "I believe in heaven."

"But you don't have to be good to get in," I said.

Skye laughed -- a piping sound, loud but not easy. ...

"I'll tell you what," Skye said. "If anything happens to me, I'll come back and fill you in. Tell you what it's like."

"Me too, you," I said.

She laughed. Growing up, she had often traveled under the imposing watch of bodyguards -- and so had faced her mortality early. She probably didn't consider me important enough for serious peril.

"Unless you get thrown from a horse," she whispered, "I don't think you're going anywhere. And even if you did, you probably wouldn't tell me anything."

"I will," I insisted. "I promise."

My eyes adjusted to the dark, and I could see Skye raise her brows doubtfully.

"Blood oath?" she said.

She opened her hand to reveal the razor blade, still resting against her fingers. I held out my hand obediently, waiting for a gentle slice of my thumb; but Skye did herself first, carving from the base of her middle finger to her wrist.

She sat up and cupped her fingers to catch the blood, which gathered in her palm -- voluminous enough to sip from. I felt a sharp rush of nausea -- the kind that usually accompanies one's own grave injury. The green of Skye's irises was almost entirely swallowed by black pupils.

"Now you," she said. "Hurry up."

I took the razor and held it over my palm. My hands didn't shake. But I did hesitate.

"Come on," Skye hissed, faintly maniacal.

"Shut up," I said. And scratched a faint, horizontal line, one third the length of hers. I had to squeeze it to bring out blood, but Skye thrust her hand into mine like our wounds were equal.

"There," she said, our hands creating one man-sized fist, Skye's blood trickling between our fingers. "It's a pact."

I got a T-shirt from my top drawer, which she wrapped around her hand. She settled back, holding the ballooned cloth against her chest like a battle veteran. If I'd been able to see in the darkened room, I'm sure her fair cheeks would have been flushed with color and an eerie sort of pride.

And I thought that whatever story we had together -- Skye and I -- she would be dead by the end of it.