Hazel eyes, verging on green.

Abby stared into them, trying not to be obvious about it, but the lips below curved into a sly smile, and she blushed. Those eyes twinkled, showing more than a hint of suppressed deviltry, and one set of lashes slowly lowered as Corina winked at her.

It was too much, and Abby closed her eyes, blanking out the cakes and their friends and the world. She needed to collect her wits; how did Corina do it?

They were the best of friends, unlikely as it might seem. Had they met later, perhaps they wouldn’t have bonded, but the preschoolers who discovered they shared the exact same birthday were too young to know how dissimilar their temperaments would become. The teenagers they were now were too close to care.

On the face of it, they were of a kind. Corina was dark-haired and olive-skinned, while Abby had blonde hair and pale blue eyes. But both were tall, for girls, and willowy in a way that drew second glances from boys who saw them. The physical similarities were accentuated by the unwritten code that dictated they and their friends all wear the same types of clothing. Indeed, their two families had noticed a tendency for the girls’ wardrobes to oscillate slowly back and forth between the two households.

Internally, they could not have been more different. Not in intelligence, not in attraction to the boys that circled them, not in obedience to their elders, but in spontaneity. Where Abby often felt crushed by the attention focused on her, it seemed to lift up the extroverted Corina; the blonde couldn’t understand how the brunette did it.

Abby opened her eyes on the party. She and Corina were eighteen years old, and they were surrounded by friends of both sexes, temporarily freed from the burden — or support, depending on how one looked at it — of parental supervision.

Because the two girls were always together, it wasn’t possible, strictly speaking, to be a friend of one and not the other. However, if Abby were to make a hypothetical distinction, she was confident nearly all of the teens around them were Corina’s friends — hers only by association. The only person she knew she could depend on looked back at her from the other side of the twin birthday cakes.

What was Corina’s secret? Abby wondered for perhaps the millionth time. It wasn’t hotness; they’d looked in mirrors more than once and agreed (objectively) they were equally well-equipped to tease boys, although the analysis was strictly academic.