Sirius started suspecting it when he realized that James never smiled.
Oh, he smiled, all right—during the daytime. After sunset, though, he would always turn away when he laughed, only give tight-lipped smiles instead of his usual lopsided grins. Even when he talked, he never showed his teeth, never at night. Of course, James always spoke extremely quickly and cleverly, but Sirius could still sometimes see a flash of white during the day. One night, Sirius found himself staring at is friend's mouth, trying to see if James revealed his teeth when he spoke instead of listening to the conversation. Not even once.
"Padfoot, are you even listening to me?" Sirius jumped and looked into James's questioning eyes. His eyes. They were the strangest color Sirius had ever seen, even more unusual than Lily's brilliant green—not really hazel, but a vibrant gold shattered through with crystalline green. In he soft candlelight, they almost seemed to glow. Sirius swallowed, shaking his head. "Sorry," he muttered.
James was always extremely pale—which was odd, considering how much time he spent outside. Well, they did live in England. But James simply did not tan. He didn't burn, either, not even in thick summer sunshine. Nothing like Snape's pasty, unhealthy skin tone, James's skin was an elegant ivory white. Maybe it was the inky blackness of his hair that made him seem so pale.
James rarely ate or slept. He wasn't anorexic, Sirius was sure, but food just never seemed to appeal to his friend. Oh, he'd eat at mealtimes, but reluctantly, as though he only did it for the sake of survival. Or appearances. He only ate certain foods, favoring red things, and often skipped meals altogether, claiming that he'd eaten in the kitchens.
Sirius would often ask why his lips were stained red, always teasing him about really spending his time in broom closets with girls, and James would always be quick to point out the lipstick mark on Sirius's cheek. But his friend's eyes were always full of relief—relief that Sirius had provided him with an excuse.
As for the sleeping, James frequently appeared at breakfast with dark circles under his eyes. He constantly complained of suffering from insomnia, but always seemed so manic at night. James was a night owl; there was no denying that. By contrast, he could be lethargic during the day, not lazy per say, just less—wired. Less predatory.
And how could James's reflexes be so amazing? Quidditch was one thing, but the messy-haired teen moved more like a cat than a person. Graceful, balanced, incredibly acrobatic—heck, James was probably the quickest and strongest person in the school. He once broke Macnair's arm during a fight and managed to outrun the rest of the Slytherin gang and two teachers. Now, Professor McGonagall was no spring chicken, but it was a bit unusual that James, tall though much more lean than bulky and very much on the lighter side of the scale, had been able to beat Macnair, who was he size of a troll, in a physical fight. It wasn't a simple fracture, either, but a straight snap through the bone.
Sirius's suspicions continued to grow, finally reaching their peak in Potions, where James had to be excused because he was allergic to garlic, which they were using. An allergy was one thing, but barely being able to stand up because of just standing next to something—that was over the line. It was Sirius could do not to cut his hand and wave it in front of James's face just to see if he'd react.
Sirius began to check himself for bite marks every night. He never found any, not a single scratch, but he still did it, just to be careful. Especially when they were doing homework, and James would lean over Sirius to read what he'd written, breathing heavily, his teeth inches from Sirius's throat—
Sirius shuddered and looked over at where James was talking to Lily. He wasn't smiling, not really, his lips tight over his teeth, his eyes flickering to her neck occasionally.
Oh yes, Sirius had his suspicions.
Author's note: This may continue into a story, I have an idea; it may stay as a oneshot. Please Review and tell me if you would like me to continue it.