doomslock:AU - School Reunion└ The Doctor poses as a substitute teacher for a week at Dean’s school.
doomslock:AU - School Reunion└ The Doctor poses as a substitute teacher for a week at Dean’s school. They form an unlikely friendship where Dean manages to trust him enough to divulge the secrets of his life. But all of a sudden, the Doctor disappears. Years later, he finds Dean once again. -- source link