Firsts
The first time Draco noticed the string was before his first year on the Hogwarts Express. He was sitting, legs outstretched when he felt a tug on his ankle. Thinking it was Pansy being overly affectionate again he went to snap at her only to see a thin red string tied around his ankle. The thread spooled outward, pooling on the floor and snaking under the door leading out of the compartment they were in.
He looked around for the string tying culprit only to find there was no one near his feet. How long had the string been there and how had he not noticed someone tying it on him? Feeling embarrassed to be so oblivious he tried to discretely remove the offending addition. Much to his dismay the string refused to be removed. There was no knot to untie and when he pulled to see if it would stretch over his foot he swore it got tighter in response. He pulled hard enough that it hurt the skin of his hands and ankle but the string wouldn't break.
Theo was the one who finally asked what he was doing. Now feeling even more self conscious he snapped that he was trying to get the damn string off and he would kill whoever had put it on him. The whole compartment quieted and Theo asked what string he was referring to. He would have thought their lack of ability to see the string as some elaborate hoax if not for his social standing in the group and Pansy's participation. She was sycophantic enough that she would never try to embarrass him in any way. Their bemused stares were enough to quiet any other comments he might have had.
Thoroughly confused and slightly mortified, he mumbled to forget about it and that he was headed to the bathroom. When Crabbe and Goyle made to follow him he regained some of his superiority and snarled that he was perfectly capable of making it there on his own.
He tried to discretely keep his eye on the string as he left the compartment, watching as it seemed to shorten as he followed it's trail. Then to his horror he stumbled upon a mass of red thread, knots and spirals littering the floor of the train. No one else seemed to notice the obstruction. After his compartment's reaction to his outburst he had a feeling that this was something only he could see.
He tried to suppress the dread swelling in him as he looked at the mass of red strewn about the floor. He didn't want to to try to unravel it to see where it would lead. He knew enough about magic to know that something strange was occurring and his eleven year old self was not yet ready to handle what it might mean.
He locked himself in an empty compartment, tumbling into a seat and shut his eyes tightly. He did not want whatever was happening. He was on his first ride to Hogwarts. He was supposed to be sorted in to Slytherin today. He was supposed to reign supreme over his peers and enjoy being the Malfoy heir. He was not supposed to have some strange magical thread tied to his ankle leading ostensibly to nowhere that no one else could see.
When he opened his eyes, the string was gone. He blinked. It was still gone. No thread around his ankle. No red spooling onto the floor or leading out under the door into the hallway. Not a fiber of red was left. But a small part of him could still feel it. He felt the slight rub of it against his ankle and the small tug to follow it wherever it led.
He shut those precarious thoughts down and decided to ignore them. He laughed at himself for making such a big deal out of what was probably nothing. He chalked the incident up to nerves. He had the weight of two pureblood houses on his shoulders and a father whose expectations were a constant shadow. Rolling his shoulders, he left the compartment to join his friends, to be the pureblood heir his father expected him to be and ignored the small part of him that felt the thread trailing behind him.
Hermione's first experience with her string occurred in the Great Hall on the same day. She had been explaining, in her best authoritative voice, the magical ceiling and how it was charmed to match the weather outside. She had just reached her left hand up to gesture above her when she caught sight of a thin red thread encircling her wrist. She let out a small shriek, earning the attention of a few of her fellow students. However, like Draco, none of her companions noticed the string and she quickly tried to change the subject to their impending sorting when they started to look at her strangely. She was quite tired of being in a freak in her muggle school. She did not want to be different here too.
While the conversation moved on around her, she tried to pull at the string but it wouldn't budge. With no knot to untie and no way to stretch the circle, she surreptitiously looked around to see where the thread led to. She caught sight of the thread weaving its way through her fellow students but could not see another end. She looked at her peers again and wondering how no one else was seeing this. She had read every book over the summer for her first year on Charms, Potions, Transfiguration and Herbology and had never stumbled upon something like this.
Professor McGonagall interrupted her silent panic, ushering them along to their sorting. Not wanting to draw attention to herself she pulled the sleeve of her robe down over the string. She observed that no one else seemed to notice it, no one was even tripping over the piles on the floor. She marveled again that she had magic in her life and swore to herself to get to the bottom of whatever was happening to her.
The string followed her to the front of the Great Hall, to the stool where she was sorted into Gryffindor, and trailed along as she took her seat beside the two boys she had shared a compartment with. She hadn't noticed it's disappearance until after the Headmaster had finished his rambling speech, she moved to pick up her glass of pumpkin juice, an odd new choice that her dentist parents would absolutely disapprove of. Her small gasp was quickly covered up by exclamations of the quantity and variety of food laid before them.
For the rest of the night she continued to touch the place on her wrist where the thread had been tied. Even though she could no longer see it, she knew it was there. In her bed that night, with the curtains closed, she ran her finger along the thread that she couldn't see and knew that this indeed was going to be a very interesting mystery to uncover.