Only one pair was still battling, apparently unaware of the new arrival. Harry saw Sirius duck Bellatrix's jet of red light: he was laughing at her.
'Come on, you can do better than that!' he yelled, his voice echoing around the cavernous room.
The second stunner had missed him by an inch, disappearing straight through the black curtain behind him. Sirius had the upper hand now. A third stunner came roaring past, but Sirius dove out of the way once again, towards the end of the dais. Bellatrix was now between Sirius and the ragged curtain.
However, Bellatrix was having none of it. She had abandoned her weak stunners now and had moved onto unforgivable curses. Sirius had realised this too and instead of using magic, he threw his wand to the side and pulled out a pocket knife he had been carrying on his person.
Harry was watching the battle take place near the veil, hoping that sooner or later, Bellatrix would notice Dumbledore's presence in the room and flee. Bellatrix had noticed that Sirius had a pocket knife instead of his wand and taunted him.
'You seriously expect to defeat the Dark Lord's most dedicated follower with that tiny piece of metal?' she cackled.
She raised her wand, a killing curse on her lips but Sirius was too quick for her. He shoved the blade into her belly and lifted her off the ground. The laughter had not quite died from her face, but her eyes widened in shock.
Then in one swift motion, Sirius threw her with the knife still in her stomach into the ragged veil. Harry saw the look of mingled fear and surprise on Bellatrix's face as she fell through the ancient doorway and disappeared behind the veil, which fluttered for a moment as though in a high wind, then fell back into place.
'The Dark Lord's most loyal follower, now extinct!' Sirius bellowed out when the veil settled down.
Sirius had a smug look on his face when he turned around and jumped off the dais. However, Harry was confused – Bellatrix had only just fallen through the archway, she would reappear from the other side any second, ready to curse Sirius for turning his back to her.
But Bellatrix did not reappear.
'Is-is she really?' Harry stuttered, unable to find words to describe what he had just seen.
'Yup. Now she cannot torture another family into insanity ever again.' Sirius replied, adding a glance to Neville.
When Harry walked into the atrium after getting off the lift with Sirius and the others, he was shocked to see Voldemort standing there, next to the Fountain of Magical Brethren. His blood red eyes were glaring killing curses at Sirius.
'So, felt the need to kill my most devoted follower just because you felt the need to disown your family for being a blood-traitor unlike them? Why am I not surprised?' Voldemort said calmly to Sirius, as though he were speaking about the weather.
Dumbledore stepped out from behind them.
'It was foolish of you to come here tonight, Tom. The Aurors are on their way.' Dumbledore deadpanned. Harry, Sirius and the others hung back.
'By which time I shall be gone, and you shall be dead.' Voldemort spat out in response.
(The following fight went the same as it did in the original storyline. Voldemort and Dumbledore duel, Voldemort possesses Harry, Fudge sees Voldemort and is forced to admit that he is back.)
'He was there!' shouted a scarlet-robed man with a ponytail, who was pointing at a pile of golden rubble on the other side of the hall. 'I saw him, Mr. Fudge, I swear it was You-Know-Who, he looked at us and Disapparated!'
'I know, Williamson, I know, I saw him too!' gibbered Fudge, who was wearing pyjamas under his pinstriped cloak and was gasping as though he had just run miles. 'Merlin's beard-here-here!- in the Ministry of Magic!-great heavens above-it doesn't seem possible-my word-how can this be-?'
'If you proceed downstairs into the Department of Mysteries, Cornelius,' said Dumbledore- apparently satisfied that Harry was all right, and walking forwards so that the newcomers realised he was there for the first time (a few of them raised their wands; others simply looked amazed; the statues of the elf and goblin applauded and Fudge jumped so much that his slipper-clad feet left the floor)-'you will find several escaped Death Eaters contained in the Death Chamber, bound by an Anti-Disapparation Jinx and awaiting your decision as to what to do with them.'
'Dumbledore!' gasped Fudge, beside himself with amazement. 'You-here-I-I-'
Fudge took one look at the place where Harry was standing and set his eyes on Sirius.
'Merlin's beard, it's Black! SEIZE HIM!' He cried upon looking at him.
'He is no more a death eater than I am.' Dumbledore interrupted as Aurors prepared to make a grab of Sirius. 'If you don't believe me, I'd suggest rolling up his left sleeve and questioning him under veritaserum.'
'I—I—Okay,' Fudge bumbled in response.
The questioning went in Sirius' favour. He was cleared of all charges and received 300,000 galleons in repayment for his false imprisonment. He was fined for being an illegal Animagus, but he was not sent to Azkaban for it as he already spent 12 years in that horrid place. The next topic of concern was Harry. Dumbledore wanted him to reside at the Dursley's so that the blood protection stayed intact. However, Sirius wasn't having any of it.
'Sirius, you need to understand that Harry needs to return to the Dursley's every summer to ensure that the Blood protection I cast over it stays intact. He needs to stay safe.' Dumbledore attempted to Reason with Sirius.
'And how is that safer than the protection that you can cast over a wizarding home?' Sirius retorted.
This argument continued for a significant amount of time in Dumbledore's office before Dumbledore gave in and decided to give the home that Sirius and Harry were going to live in as much protection as possible. The house was under a Fidelius charm with Dumbledore as secret keeper. Knowing that the Dursley's were going to be a target of Lord Voldemort, Dumbledore decided to move them to a safe place.
Storyline Summary:
Harry and Sirius spent the next summer together. Near the end of the summer, Dumbledore showed up, sporting a blackened hand to collect Harry to persuade Horace Slughorn to come out of hiding and teach at Hogwarts once again. Sirius was livid when he found out that Snape was going to be the next DADA teacher. The rest of the next school year pretty much played out how it did in Half-Blood Prince, except Sirius was present in Dumbledore's private lessons with Harry. Snape murders Dumbledore atop the Astronomy Tower as he did in the original storyline.
When Harry shows Sirius the fake locket, he recognises the R.A.B initials straight away and asks Kreacher for the locket before Kreacher could give it to Mundungus Fletcher, making the break-in fiasco at the Ministry unnecessary. The Horcrux hunt goes successfully as it did in the book. However, since Yaxley never saw Grimmauld Place, they never had to go on the run, which basically means that Draco is still the master of the Elder Wand. Sirius was able to access the Lestrange's Vault, so he got Hufflepuff's cup easily.
The Battle of Hogwarts went almost the same way as it did in the original storyline, Remus and Fred were killed. However, since Bellatrix fell through the veil instead of Sirius, Tonks survived the battle. Harry managed to disarm Draco in the room of requirement, which means that the Elder Wand changed allegiance to Harry. Voldemort kills Snape, hoping the wand would become his. Peter Pettigrew cornered Harry, however his hand suffocated him to death because he hesitated.
Harry sacrifices himself in the forbidden forest. Sirius was hysterical when he found out this fact, however Harry reveals himself to still be alive and faces off against Voldemort. Teddy Lupin was raised by Tonks, with a bit of help from Harry, Sirius and Andromeda. Harry and Ginny married as per the original storyline and had three children. James Sirius Potter, Albus Severus Potter and Lily Luna Potter.
Instead of hiding it at the Ministry, Sirius hid the Time-Turner alongside all the forgotten junk at Grimmauld Place and had ordered Kreacher not to touch it. Which means the Cursed Child fiasco never happened.
The end.