Everyone thinks it's Remus. He knows that. He has no way to prove them wrong. James said they would never treat him differently just because he was a werewolf, but that was the biggest lie he'd ever heard.
Of course it wasn't Remus. He would never betray his friends like that. James, his best friend, one of the first people to see past his condition. Sirius, his lover, his world, the one who became an animagus for him, and convinced the others to do so as well. Peter, the friend he could count on to help him. Peter always helped with Remus's problems the best he could without suggesting some elaborate prank.
How could he betray his friends, his family? He would never even think about that. It hurt that the others would.
Even Sirius believed that it was him. He grew distant, cold. He would never give a proper good bye when one of them left their shared home for a mission.
They used to stand at the door and hug, their foreheads pressed together like they would never see each other again. Remus would say "I love you," and Sirius would reply with, "to the moon and back." That's how they always did it.
That was how they did it up until that night. October 31st, 1981. Remus came home from a mission, house empty. Something felt off. He didn't know why it felt different, but something was definitely wrong.
He got a phone call from Mary. Her voice was sad, hoarse, like she had been crying. Five minutes into the phone call, he dropped the phone, the wire catching it in the air.
James, Lily, Peter. They were gone. It was Sirius. It was always Sirius. It was Sirius who had told Voldemort, Sirius who killed the McKinnons, Sirius who killed Peter. Sirius, who had killed a part of Remus.
No wonder he had become distant, no wonder he had become cold. He was a Black after all. He had done this before, how could Remus have missed it? It was Sirius who had told Snape Remus was a werewolf, so why wouldn't it be Sirius who had told Voldemort where James and Lily would be?
Remus wanted to prove them wrong, but the evidence was there.
Remus hated Sirius. Or at least that was what he told himself. He hated him for what he'd done, for how he'd blamed Remus, for everything. But deep down, he still loved him. It made him feel so horrible, so guilty, because how could he love someone so evil?
Remus had no choice but to carry on. It was difficult, harder and more painful than any full moon. How could he live without them? His family, his friends, the one who got him through everything, no matter what.
He developed horrible habits, drinking, smoking. But he didn't care. Who did he have in his life to tell him to quit? Who did he have to help him? To stop him? No one. Not a single person.
~~~
After the war, everyone was celebrating. What did Remus have to celebrate? The loss of his friends? The loss of his lover? The loss of himself? Every year, Halloween got harder to celebrate. After that awful day he never celebrated again.
~~~
It was all over the news. Sirius Black has escaped. Remus didn't know whether to be angry, sad, or happy. In some ways he felt all three. He was angry that Sirius had escaped, for reasons unknown to Remus. He was sad, because he was heavily reminded of that day. But he was happy, because tr chance to see his lover had resurfaced.
~~~
After twelve years he started getting better, and took a job as a teacher at Hogwarts. He started a day after the full moon, so he slept on the train. He woke up to dementors, and... James? No. James was gone. This was Harry. James's son.
Remus taught Harry, taught him how to get rid of dementors, taught him how to repel boggarts. Harry became Remus's favorite student. Harry reminded him so much of James sometimes that it hurt. Except his eyes.
He had Lily's eyes, and he saw nothing but her when he looked at them.
~~~
It was the last full moon of the year. Like usual, he was tired, sluggish, and easily annoyed, so he stayed in his office. Until he saw Sirius on the map.
He stared at it for a moment. He was transfixed. Then he looked again and saw Harry, Hermione and Ron. But right beside Ron's name, was Peter. He grabbed his wand and rushed out.
~~~
The tree was never a problem for him. He simply cast a spell and continued on. He burst through the door and saw Sirius on the floor, Harry above his with a wand. He acted on instinct, casting Expelliarmus when he saw them. He knew the truth now. He immediately embraced Sirius, making up for all the time they missed, all the time they lost, all the times Remus believed it was Sirius.
But it wasn't Sirius. It was Peter. It was always Peter. How could it not be, it all made perfect sense. Peter ran away. Peter betrayed James and Lily. Peter ruined everything.
~~~
Remus forgot about the moon. He forgot about it until it was too late. He didn't know any better as a wolf, he couldn't help but attack people. It was in his nature. Only as a wolf, of course. He attacked Sirius. He attacked Snape, although he wasn't too upset about it. He tried to attack Harry.
Remus was livid. Dumbledore knew, and he let Sirius rot in prison for twelve years. Dumbledore knew about the secret-keeper plan. He knew Sirius and Peter switched. While he may not have known Peter was the traitor, he knew Sirius was innocent for all tr twelve years he let him sit in that jail cell and rot.
Remus quit. He couldn't stand working for someone who could let an innocent man suffer. Not just any man, but Sirius. He wasn't a Black at all.
After he quit, he and Sirius joined the Order of The Pheonix. They cleared out Grimmauld place, using it as headquarters. They cleared out every room. Every room except for Regulus's. Remus didn't say anything about it to Sirius, but Remus knew what he was doing.
~~~
Harry got put in The Tri-Wizard tournament. Sirius helped him get through the tasks, as well as his friends. But nothing could prepare them for the last task.
Voldemort was back. The reason behind all this torture, this pain, this misery and grief was back. Yet nobody believed it. Remus understood why, but sometimes you have to deal with a truth that causes pain.
~~~
Harry came to the Department of Mysteries. He thought Sirius was there. It was a trap. So of course Sirius went. He had to save him. Remus and the other aurors went as well. Remus wished he could stop Sirius from going.
It was Bellatrix. His cousin. Sirius hated her, and for good reason. When Sirius got hit with the curse everything seemed to slow down. Remus had to hold back Harry, but his eyes never left Sirius as he went into the veil. His eyes never left his, so he saw Sirius whisper "I love you." Then Harry ran off, and Remus stood there, whispering to Sirius even though he couldn't see or hear him anymore. "To the moon and back."
~~~
Dumbledore died. Remus didn't even care. How could he, when Dumbledore was the cause of Sirius's pain, along with so many other people's. Along with Remus. He couldn't be sad about that.
~~~
The Battle of Hogwarts. Remus would fight no matter what. But when he saw Antonin Dolohov attacking Madam Pomfrey, he had to do something. Poppy had always saved him, always helped him no matter what. It was his turn to save her. He didn't see the curse. He didn't feel it when he was hit. All that mattered was that Poppy was safe.
~~~
He saw Sirius. He saw James. He saw Lily. He immediately ran to Lily, pulling her into a huge hug. Lily had always been there for him, almost as much as Poppy. After Lily he hugged James. James was like his brother. Of course he had missed him like one. He hugged Sirius last, and for the longest. His love. Sirius told him he saw it when Remus whispered back, as Sirius was falling into the veil. He heard it. He felt it. He loved it. He missed it.
Thy all came back for Harry. He brought them back, only for a little while. But he saw his parents. Harry immediately went to Lily. Of course he did. It was devastating to watch him reach out to her, only to feel nothing, as if she wasn't there. The look on his face was heartbreaking.
Harry beat him. He survived the curse again. All thanks to Narcissa. When Sirius saw that, his jaw dropped, then was quickly replaced with a smile and happy tears. He had never hated Narcissa, not like he hated Bellatrix.
When Bellatrix died, Sirius was so dramatic. He was ecstatic. Punching the air, encouraging Molly, screaming 'YES!' when Bellatrix died. It wasn't wrong to want that either. Bellatrix killed Sirius, so it's understandable Sirius would want someone to avenge him.
After the war, the Marauders were back. Lily took the place of Peter. They were happy together. For the first time in a long time, Remus was happy.