Standing in a drift of old snow outside the Constance Billard School for Girls on East Ninety-third Street, Aaron Rose waited for Serena to come hurtling through the towering royal blue school doors and into his arms. Mookie, his brown-and-white boxer, sat panting beside him on the sidewalk wearing the red-and-black plaid doggie jacket Serena had bought him yesterday at Burberry. In Aaron?s hands were two steaming cups from Starbucks. Ever since they?d gotten together at Serena?s wild New Year?s Eve party six weeks ago, this had become their little ritual. Aaron would meet Serena after school and they?d amble down Fifth Avenue arm in arm, drinking soy lattes and stopping now and then to kiss. New Year?s Eve had been a total fuck-it-we?re-both-in-the-mood-so-why-not-hook-up? spontaneous sort of thing, but over the past month they?d spent every out-of-school moment together, and they were now known as the best-looking and most adorable couple?well, threesome, if you included Mookie?on the Upper East Side. Suddenly a ray of bright winter sun flashed on Serena?s cool blond head as she pushed open the school doors, skipped down the stairs in her Stephane Kelian brown suede boots and navy blue Les Best pea coat, and stepped out onto the snowy sidewalk. Her whole face glowed with angelic excitement when she caught sight of Aaron and Mookie. ?Hi, pup!? she squealed as Mookie wriggled up to her and nuzzled her cashmere-gloved hands. She squatted down and let the dog lick her face as she stroked his head. ?You lookso handsome today.? Aaron watched them with a lazy sense of pride.Yep, that?s my girlfriend. Yep, isn?t she gorgeous? Serena stood up and threw her arms around his neck. The air around them filled with the heady, sandalwood-and-patchouli?based scent of the custom-blended essential oil mixture she always wore. ?You know what I?ve been thinking about all day?? she gushed, planting a kiss on Aaron?s thin, dark red lips with her full, peach-glossed ones. Aaron splayed his feet to keep from stumbling backward and spilling the lattes.?Me?? he guessed. Serena was the type of girl who gave herselfentirely to whatever she was into at the moment, and for the time being she just happened to be into Aaron. It had kind of gone to his head. She closed her eyes and they kissed again, deeply this time. Behind them, girls in neat wool coats and tall leather boots spilled out of the school doors, shouting giddily. A few of them huddled together to watch in awe as Serena and Aaron continued to kiss. ?Oh my God,? whispered one eighth grader, swooning in the presence of such coolness. ?Do you see what I see?? Mookie pawed at the snow and whined impatiently. Serena rubbed her cheek against the scratchy alpaca wool of the gray-and-purple sherpa hat she?d bought for Aaron last weekend at Kirna Zabete in Soho. She loved the way his cute dark brown dreadlocks poked out from beneath the earflaps. Everything about Aaron was so adorable, she just wanted to eat him up with a spoon! ?Of courseI was thinking about you,? she said, taking her latte. She cracked open the lid and blew on the sweet, steaming liquid. ?I was thinking we should get tattoos.? She paused, waiting for Aaron to respond, but his soft brown ey............