Early on a Saturday morning, before most students were awake aside from 7th years wanting an early breakfast before leaving the grounds for the day. 16 Year old Harry and 17 year old Hermione walked into the great hall wearing Acromantula silk robes bearing the crest of House Potter. Dumbledore was stunned to see the crest of Harry's robes surrounded by 2 gold embroidered circles, indicating he was The Potter of Potter, to be addressed as Lord Potter. Even more surprising was that Hermione's robes had the crest surrounded by 2 silver circles, she was the Lady Potter!
This could not stand! His plans required Harry to be married to Ginerva Weasley! He needed Harry tied to a family beholden to him, especially as Dumbledore had used Harry's money to pay the Weasley's Hogwarts fees.
He had penned a betrothal contract for Harry to wed young Ginny. He knew it wasn't legal, but counted on Harry not knowing that as he had been very careful to make sure Harry was kept ignorant of his Lordship and anything related to Wizarding law. How had he found out? How had he taken up his lordship? How had he KNOWN to? The headmaster's gaze snapped to Miss Granger, no... Lady Potter. Obviously, they were married and just as obviously she needed to be eliminated.
He looked at Severus and allowed him to read his surface thoughts. 'Severus, Granger needs to be eliminated.'
Severus replied the same way. 'I will goad him to challenge me a duel, he will use her as his second. After I stun the brat, I can kill her.'
Harry and Hermione approached the Gryffindor table, but were intercepted by Dumbledore and Snape who had come down next to the wall behind the Gryffindors.
Dumbledore started to speak "Harry, my boy_"
"That's Lord Potter to you." Interrupted Harry.
The headmaster blinked 'Where is this antagonism coming from? What does he know?'
"Surely Harry there is no need for such formality." He said, eyes twinkling.
"You are of course correct headmaster; my friends can still call me Harry when appropriate." He paused and looked directly at the headmaster. "You can call me Lord Potter. I have taken up my Lordship and assumed all rights and responsibilities that that entails."
"I'm sorry Harry, but as your guardian, I cannot allow that." He twinkled in a grandfatherly tone.
"Really? I'm sure you were made aware that being forced to compete in the Triwizard tournament emancipated me, funnily enough, I didn't receive my own copy of the notice. And aside from that, magic never recognised you as my guardian, my godfather specified in his will that I be emancipated and finally, my parents will, which you illegally sealed also specified that I be emancipated at 16. Lastly, Magic has recognized me as the Potter of Potter. He held up his hand and the Potter Lord's ring appeared on his finger. You told me that I needed to embrace Britain's magical culture," here Harry smiled thinly, "so I did."
Dumbledore realised he had made a mistake initiating this confrontation in the great hall. He needed this to continue in a less public setting. Harry knew far more than he had expected. Things that Dumbledore would have been happy if Harry never found out. He imperceptibly signalled Severus to create a distraction.
"Just like your father, a pompous peacock! And you married the Mudblood whore!" sneered Snape.
The entire great hall gasped in shock!
Harry turned to Snape. "I assume you have been schooled in the proper forms?"
Snape sneered a nod.
"Very well. I will give you one chance, apologise." Said Harry calmly.
"Apologise to a Potter? An uncultured buffoon, like you? Never."
"I see," said Harry, turning to Dumbledore. "Headmaster, what does the law state about insulting the Heads of an Ancient and Noble house?"
Dumbledore paled, the archaic, but still valid, law stated that the head of house could take whatever action he considered appropriate, including killing the person if the offender refused to apologise. He didn't even have to give warning.
"Harry, Professor Snape has my full confidence, I am sure he didn't mean it." Dumbledore prevaricated.
"That is your final word on the matter?" Harry replied.
Dumbledore nodded with a grandfatherly smile.
Harry turned to Snape and said clearly "I gave you a chance to apologise."
After that comment, Harry's hand, which had been at his waist, pulled a Bond Arms Defender double derringer from the disillusioned holster on his belt in a blur of motion. Cocking it as he raised and extended his arm. From a range of 2-3 feet, he fired. The no. 4 shot from the .410 shotgun cartridge struck the potions professor near the bottom of his ribs on the left destroying them before shredding his heart. Dumbledore along with all the others present froze, dumbfounded at Harry's actions.
Eyes wide and wild, Snape collapsed to the ground, staring at Harry.
Harry moved to stand over the Professor as he calmy cocked the pistol's other barrel.
"I'm sure mum will have words with you on the other side about the way you have treated me."
With that, Harry aimed the pistol and fired the second barrel. The .45 hollow point round punched into Snape's forehead.
Harry turned to Dumbledore as he reloaded the derringer, the headmaster's eyes slowly rose from the messy body of his now former potions master. Shaking, Dumbledore stuttered. "H-harry, what have you done?"
"Defended myself and my wife from your machinations" replied Harry coldly as he snapped the reloaded weapon closed. "Why do you ask?"