the_debt_of_time

"It's none of your―" Sirius turned, eyes narrowed, when his ears picked up
something. He spotted a brief flash of red through the dirty window of the building. "Did
you see that?"
Upon bursting through the door, he and Kingsley were met with, not underlings,
but fully marked, cloaked, and masked Death Eaters shooting curses left and right. Peter
and Mary were nowhere to be seen, and Wilkes did not seem to be there.
Instead, Sirius saw James and Lily facing off against four Death Eaters. From the
sound of the cackle coming from one of them, he knew Bellatrix was there. Another had
long, blond hair peeking out from behind the mask, and Sirius growled.
"Malfoy."
"Longbottoms, backup Potter and Evans!" Kingsley ordered. Suddenly, Alice and
Frank came into Sirius's vision, rushing off to the battle. "Black, find Pettigrew and
Macdonald!"
Sirius nodded, despite everything inside of him needing to be at James's side. He
watched as Alice and Frank jumped into action, protecting each other as they moved
toward James and Lily. Only then did he notice that the other two Death Eaters were not
actually fighting. One was throwing hexes so far out of the line of battle, Sirius wondered
if there was someone to the far right that he could not see. The other was duelling properly,
in a familiar style, only from the angle Sirius was looking, it looked as though he were
purposely deflecting curses that were being sent at Lily and James from Bellatrix and
Malfoy.
"Don't just stand there, you idiot!" Malfoy shouted from beneath his mask at the
smallest Death Eater in the group. He reached forward and gripped the masked wizard by
the throat and threw him violently to the side where he collided with the corner of a door.
As he hit the edge, his mask cracked and fell from his face, and Sirius's eyes widened.
A mirrored pair of grey eyes looked up into his face.
"Sirius," Regulus whispered, and his face drained of all colour.
"You!" Sirius snarled and aimed his wand at his younger brother, gaping at the boy's
robes that had been pulled up in his fall to reveal the Dark Mark as clear as day. Sirius's
stomach turned at the sight, and he threw a silent Stunning Spell at his Death Eater sibling.
"Regulus, you bloody prat!"
"Sirius! Stop!" Regulus pleaded, throwing up a shield.