Disclaimer: Harry Potter and Co are property of J.K. Rowling. Many thanks for her story.
They would never know.
He stood above the crowd of solemn students, watching with a cold expression as everyone waited for him to speak. It had always been this way, with his students cowering in fear, trying not to slip up and be the one he would lash out at next (who wouldn't berate someone who though adding the hairs of murtlap before the skin of a flobberworm was the correct way to make a Blood Replenishing potion). The power he held over them was great and he never hesitated to use this to his advantage. This time he used it to keep them all safe from those two, though they would never know.
Then green eyes flashed his direction one day and he knew everything had changed. He could use his intimidating nature to cause all surrounding students to cringe, but not once did the angelic eyes turn away. Not once did the face of the devil show fear or submission (just the thought makes his long, stained fingers curl). Not when he stormed into class on the first day, robes billowing behind him, with every intention of singling him out and revealing the boy to be just like his father. Though his face was soft with childlike innocence, green eyes ("The most brilliant shade of pure green, shot through with specks of gold," he had once told her) shone with energy and boldness. With the more childlike face of the father and ethereal eyes of the mother, he calmly disobeyed every rule he had established. The soft voice and brilliant gaze made him to feel (whether it be good or bad), and that made him angry.
Just like his father.
Even now, now that he has emerged from the sea of black robes and weary students, now that he has finally come and the end is near, the same defiance straightens his spine. His lips rise in a sneer at the sight of the boy (man) before him. He is ready to face the darkness ahead. His eyes, which were so green (not like hers, he had realised in fourth year as he stood so close to him), were ablaze with defiance and betrayal.
Just like his mother.
And now those eyes stare down at him from above (an angel's eyes, though this angel cannot save him) in disbelief and sorrow. For him. He begins to use his last remaining energy to liquefy the memories he wandlessly summons forth. It pours and (this is the end), through the blood and the pain can only manage to croak three small words. Green eyes meet his once more (don't leave) and with his last wish granted (those eyes, staring at him with something other than contempt, have actually started to blur with tears?), he can finally acknowledge the truth.
That he would give everything for this boy (Death has appeared and is holding out his pale hand), the one that is so much like her and is simultaneously his own person. He would give his life for him, (he wishes to look into the green for a moment longer, but knows he cannot) for this boy with the face of the devil, but the eyes of an angel, because he has at long last realised that he is not his father and never was, no matter how he appeared. Everything was for him. For her. For them.
They would never know.