WARNING: SPOILERS!!! ~A Watty's 2019 Submission!

Saved for Karina Potter, Aunt Marauder

Karina made sure that all the students had left the courtyard, before going over to the humped witch's statue.
"Dissendium." She whispered, tapping it with her wand and the old corridor revealing itself. She grinned, before going down into the old tunnel, shivering. It looked like it hadn't been used in ages, covered in moss and -gulp- tiny animal carcasses! She hurried further into the tunnel, wishing for the earlier days when this tunnel had been a bit tidier.
"Sirius?" She called softly, casting Lumos. "Pst! Sirius! Where are you?" That was when she heard a hissing noise, and saw a snake coming towards her! She screamed and tried to run the other way, but was stopped by something she couldn't see as her wand went out! The thing grabbed her wrists, stole her wand, and she heard "Stupefy!" The hissing stop, and the came, "Lumos." When the light came back, she saw him. His appearance had changed some. He had a beard that was matted and long and dirty. He could used a haircut, and his robes were a disaster. But, behind the vagrant appearance, Karina could see into his big, brown, tired eyes, and see her Sirius Black.
"Sirius!" She breathed. He was panting too.
"Karina!" She jumped up into his arms and they kissed. "Oh my god!" He panted as they kissed over and over again. "I thought that I would never see you again!"
"I thought I would never see you again!" She told him. "Merlin's beard, I missed you!" He hugged her close.
"I missed you too, Karina. So, so, so much!" Then he pulled away and looked behind her.
"Where's Harry? I thought you'd bring him with you." She shook her head.
"I thought it best to keep our secret tunnels between us and the Weasley twins." Sirius raised an eyebrow. "Those two would give you and James a run for your money! I saw that they had the Marauder's Map, probably stolen from Filch. They use it to sneak off to Honeyduke's through here and buy treats." Sirius shook his head, but was laughing.
"Those two. James would have loved to meet them!" She hugged him again tightly, then stood before him.
"We only have a short time! Remus and I have a break for only an hour, and I-!"
"Remus? Remus is here too?" He asked excitedly. "Why didn't you bring him down here?"
"Because Remus also believes you killed Peter!" She said, exasperated, then began to hit his chest playfully. "Now! Tell! Me! What! Happened! That! Night!" Sirius laughed and grabbed her wrists, stopping her.
"Alright, alright!" Then he took a deep breath. "Peter was the one who killed all those Muggles! He's been alive and hiding as a rat for years!" Karina gasped, and Sirius nodded. "And that's not all! You know how they said all they could find was Peter's finger?" She nodded. "He cut it off himself! And, get this, he's the Weasleys' pet rat! I saw him in the paper!" Karina's eyes went wide.
"Really?" She said, thinking back to Ron's pet rat, Scabbers. He was missing a toe. And Crookshanks did seem to go for him more than any rat she'd ever seen...
"What do we do?" She asked him.
"Bring me that rat." Sirius told her. "I'll kill him myself!"