This is set instead of the deathly hallows book but with Sirius still alive.

Chapter1:

It was in the middle of the order meeting that the death eaters stormed Grimauld place. With Dumbledore (the secret keeper) dead, they managed to gain access to it and raided it. There was a brief battle before the order members apparated away to the burrow where they set up their new headquarters.

It was around 10am when the residents began to stir. Half an hour later they were all gathered around the breakfast table eating. There was a meeting scheduled later that day and soon, the Weaslys plus harry Hermione and Sirius began getting ready.

Remus came first, followed by Mad eye, Tonks, Shaklebolt and Minerva McGonagall. 15 minutes later there was a knock at the door, Sirius opened it to find Severus Snape stood outside. Before Sirius could reach for his wand Snape took it and dragged him outside.

'I need to talk to you', he said.

Sirius clenched his fists 'you killed him, how dare you show your face here after what you've done.'

'His death was organised I assure you' Snape continued calmly before lifting his right sleeve to show the order symbols engraved on his arm, had he been a traitor, they would have disappeared and Sirius knew that well. When he spoke, he was more calm but still sounded pretty annoyed

'So why are you here?' he asked. There were so many questions he had to ask, but he knew there was little time.

'I need you to be the Hogwarts potion master now I've become headmaster' Snape said simply.

Sirius laughed. 'Me, potion master?! Why? I hate potions.'

'I know but the Carrows are coming in to teach defence, and Voldemort expects me to run the school well…'

He didn't need to continue, Sirius knew what he meant Voldemort would expect Snape to run it as if it was a concentration camp or a death eater training centre and he would need someone on the other side to help the DA.

'Sure alright, I'll do it.' Sirius agreed.

Snape nodded curtly and they shook hands putting all their past differences aside, well most of them anyway. And with that Snape turned and dissaparated as Sirius made his way back indoors.

What was that all about? Molly Weasley asked

Sirius sat back down at the table beside Ron.

'Snape. Is with us after all, his arm is still marked, apparently Dumbledore's murder was organised. I didn't have time to ask all the questions I would have liked but he's going to be headmaster and wants me to take the potions master post to help the DA.' Sirius said

Remus laughed. 'You, a potions teacher?!'

'You'll probably be the youngest teacher in Hogwarts History' Fred said

Since although Sirius was born at the same time as Remus and James, when he was sent to Azkaban, they performed some complex non ageing spells on him so that while in prison he would not age and would spend eternity suffering, meaning that he was still 19 when he escaped making him now 22. He smiled at that

'So, what else is going on' he said as the order meeting continued

'Bill and fleur are getting married next week and want to have the wedding here' Molly said.

'Now, molly, do you really think that's a smart idea?' Kingsley asked sympathetically.

'No, no I don't but they are adamant.' She replied.

'Maybe it's good, we can have some fun for a while, pretend that it's alright for once, that we don't spend our days talking about who died today and whether or not we'll be alive by the end of the week,' Ginny said.

They agreed, the past year had been hectic with the death eaters and Voldemort gaining power.

'I think it's a great idea, have some fun before we leave' Harry said.

They knew that Harry, Ron, and Hermione had a mission from Dumbledore and that they had to carry it out. It took a few arguments for everyone to realise that it was important and that they shouldn't stop them from going, besides, Harry still had Sirius' mirror so it's not like they would disappear off the face of the earth.

About an hour later, the meeting was over and the members left. Fred and George were in their room when Sirius walked in. He sat at the bed and examined the box of instant Peruvian darkness powder. It would darken the room and make it impossible to see anything for 5 minutes.

'You know, he said, you can increase the time of these things.' He said

Fred and George looked up at him.

'How?' They asked

And with that, they began experimenting together and improving their products. The twins were astounded by Sirius' plans. He laughed as he began working on the skiving snack boxes '

I'm not a marauder for nothing you know'. Sirius smiled.

Fred and George looked up at him, 'you mean the marauders map? The creators of it?.' George asked,

'Yeah, that's the one, it was James, Remus, Peter, and I who created it.' Sirius replied

'You guys are our heroes, we nicked the map from Fitch's office in our first year and it saved us so many times' Fred grinned,

Sirius smiled, 'Glad to know our efforts didn't go to waste' he said.

'Hey, after this is all over,' Fred began,

'Do you wanna come work with us at the joke shop?' George continued.

Sirius grinned, 'I'd be honoured to' he replied happily

The days building up to the wedding were uneventful, in a way they were all thankful. In this case no news was good news. Fleur and her family arrived the morning of the wedding and she went into Percy's old room to prepare. Harry and Ron went to try and get the tents up with Bill and Sirius and the order members were arriving. By noon, the party had begun, they were all dancing and having a good time. About two hours into the wedding, they got a patronus message from Kingsley.

'The ministry has fallen, Scimgeor is dead, death eaters on the way.' It said.

It was madness. Guests began apparating away as the death eaters appeared. Ron who was battling a fearsome death eater was shoved aside by Sirius.

'Take harry and Hermione and go. This is your only chance' he yelled.

He stunned the death eater as they disappeared from the scene. More order members joined the fight and the tide slowly turned in their favour.

The next day at the burrow, with safety in question, the remaining Weaslys and Sirius began leaving the area. Fred and George went to their Diagon alley apartment Bill and Fleur were on their honeymoon and Charlie in Romania. Sirius and Ginny left for Hogwarts leaving Arthur and Molly who insisted on staying.

As Sirius and Ginny journeyed to Kings Cross, they couldn't help but notice how it was all different. The skies seemed permanently grey and everyone was scared as they got on the train. Sirius made his way to the teacher's compartments and sat down. He nodded curtly at Snape as he came in. Soon the train was moving and the teacher's meeting had begun. Sirius tried not to fall asleep as they discussed education programmes but became more interested as they began talking about the patrol times. He had patrol every Sunday from 8 until 2am and if he were to catch anyone out after curfew he was supposed to take them to the Carrows who would administer the punishment. He doubted he would do that, the Carrows were nasty pieces of work. Alecto would teach the dark arts (he doubted there would be any defence) and his sister taught muggle studies (aka muggle hatred) which was obligatory as was going to Hogwarts.

The train arrived and everyone made their way towards the great hall. He noticed that the happy atmosphere that usually came with this event was replaced by a sense of dread and fear that lingered in the air. He knew why Snape asked him to come. There would definitely be rebellion and he was going to organise it all. The thought made him smile as he took his seat in between Snape and McGonagall. Snape stood up and gave a brief welcoming speech which was anything but welcoming and the feast began. The dismal house elves brought in the food and they ate. Afterwards Snape stood once more and sent them to their common rooms for the night where they would sign in and go to their dorms so that they would know who didn't turn up. Sirius made his way up to the teacher's quarters where he lay on his bed.

The next day he was in the dungeons with the 7th year slytherins. The worst way to start the day.

'Open your books to page 8 and begin brewing the draught there' he said curtly.

The lesson wasn't that bad, even though his name had been cleared after the battle of the ministry he was still feared. The only two stupid enough to try something were Crabbe and Goyle. They had some instant darkness Peruvian powder and decided it would be fun to throw it. Sirius had spent the summer working on it with Fred and George so instantly the darkness cleared revealing an unfazed Sirius.

'See me at 7' he said a touch of amusement in his voice worried them both slightly. They practically ran when the class was dismissed.

Next came the Gryffindor 7th years. They were brewing the same draught and this time Sirius came around to inspect the potions. He stopped at Neville who sat at his desk making a downright mess of his potion. Neville expected Sirius to shout or at least criticise him but he did neither. He merely walked up before leaning on the desk and lifting his right sleeve slightly so that his order of the phoenix symbols were showing before slowly whispering

'How's the DA.'

Neville merely replied. 'Room of requirement 7pm tonight be there.'

Sirius nodded grimly before turning his attention to Neville's potion to make it less suspicious.