the_debt_of_time

"My Muggle family was attacked by Death Eaters years ago. When they were...
gone, and I found myself without a family, the Potters adopted me."
"Is that your big secret?" Mary asked with a smirk. "Mia, you don't think we'd think
poorly of you because you were technically Muggle-born, do you? If that was so, then we'd
have hexed Lily years ago."
Lily smirked. "If I didn't hex you first."
Mia laughed and shook her head. "No. I know you'd all be my friends, no matter
what. I was attacked as well, you see." She cleared her throat nervously. "It left a permanent
scar on my body—one that can't be glamoured. However, when I came to Hogwarts,
Professor Dumbledore was able to procure a potion that would hide the scar from
everyone else. Unfortunately, it had a time limit."
Remus had informed her that some version of the truth would be best, and she
understood. The best lies were based in truth.
"Unfortunately, it appears that time has run out, and my scar has resurfaced."
"It's okay, Mia," Remus said, placing a hand of support on her shoulder.
"Remus knows?" James inquired, surprised. "I mean, when we were young and I
saw―" He gestured to her ribs. "I asked Mum. She told me that when they adopted you,
she and Dad agreed to let you start life from scratch and that if you wanted to share your
past, you would. I just... How come Remus knows but not me? I'm your brother."
"Remus was there when the potion wore off," Mia explained with a shrug of her
shoulders, not knowing how else to placate her brother. She took his hand and squeezed
it tight, glad when he squeezed back, looking slightly reassured. "And, frankly, after seeing
his reaction, I wanted him to be here when I showed the rest of you. Please don't panic."
James sat up straight, and Mia noticed that Sirius did the same, looking more on
edge than ever. With great hesitation—and a last minute concern over whether she should
just Obliviate the lot of them and wear long sleeves from that point forward—she pulled
the sleeve of her blouse up, revealing the purple scarred word in her flesh.
They each reacted exactly how she had assumed they would.
Lily gasped at the sight of it and practically shoved James out of the way to pull Mia
into a sympathetic hug. Mia could feel her friend—her sister—shaking and wondered if Lily
was afraid something similar could happen to her.