S.S
He knew Hogwarts like the back of his hand. However, he needed to visit with Dumbledore. He attempted to see him, but he was informed that he had taken a leave of absence for the beginning part of the year. He had no idea where Dumbledore went and he had no memory of it. His office would not be in use and therefore he could use. The first and most important thing he came to do was to warn Dumbledore. He placed his memories in a vial for him and spelled the vial seal, protected, and only able of being open by Dumbledore.
As he sat in the headmaster's chair and thought what he should do next. He hadn't met to speak to Lily. He had only meant to give his younger self a fighting chance. But now, seeing her and talking to her, he couldn't help but want to make himself younger and be his younger self with her. It could change everything.
He could use the time turner to the point before James and Lily's wedding. He could object. But then again the events of the next few weeks were crucial to ensure the friendship. He knew he couldn't take Lily away from James of the future would be drastically different. But he could be her friend...couldn't he?
He stayed to formulate his plan which entailed two options either being a teacher and coaching the younger him OR put the younger him into a deep sleep that allowed him to age inside. He could hide him in Dumbledore's office undisturbed until the moment after he ( the original Snape) used the time turner.
He would explain to Dumbledore in a timed letter of the boy's resting place and the memories he aught to have and anything else that should added. He needed his younger self to stay alive lest he die now in the past.
He decided on the latter. He brewed a youth potion and a deep sleep potion. As brewed, he noticed something red on the top of his cloak near his elbow- a strand of red hair. He smiled. He thought himself- I can't believe I forgot how much her hair use to get all over the place. He picked the strand ever so gently and felt it between his fingers. How could something so small bring so much happiness, and then the air caught it and it was gone.