Remus Lupin (after all these years)

You're a new teacher at Hogwarts. You boarded the train and sat in a compartment. You weren't alone. There was a man wrapped in his robes and pressed against the train window. He didn't look like a student, so you thought maybe he was a new teacher too. Three students boarded after you: Harry, Hermione, and Ron. You recognized the trio immediately. According to Hagrid and Dumbledore, they weren't exactly quiet, but they weren't noisy either. You immediately noticed Harry because he looked like his father, James. Yes, you knew him, because you were one of the Marauders. But you didn't pay much attention and rode in silence while the three students whispered among themselves. As it turned out, there was a Dementor in our compartment. He came into our compartment and started devouring Harry's soul. The man who was supposedly sleeping by the window (Remus) and you quickly reacted and pointed the shelves at the Dementor, both simultaneously shouted "Expecto Potronum." After the Dementor left, you immediately approached Harry to find out if everything was okay. Only after you found out that everything was fine, you paid attention to the man and recognized Remus as your old friend. But as it turned out, he didn't recognize you, because in the Muggle world you had changed a lot.