Disclaimer: Sadly I don't own anything...
Warning! Contains implied INCEST. Don't like, don't read!
Sirius
I run through the forest as fast as my four legs will take me. Squirrels and rabbits scurry away from me; I am a predator to them. I don't know where I will end up, but I don't care. Anything to get out of that house, that prison that I prayed never to go back to. But they keep me locked up there, safely in hiding. I'll show them, I think. I can take care of myself.
Suddenly a loud Crack pierces the air, loud to my keen ears. I dart behind a tree, changing quickly back to my human form. Wordlessly I conjure robes out of thin air and put them on. Then I wait silently.
Bellatrix
I materialize in the forest with a loud Crack. Though I don't see him, I know he's here. I laugh softly. "Come out, come out, Sirius," I call. I hear a noise, and Sirius steps out from behind a tree; his face is unreadable.
"Bella. How nice to see you again." He smiles sarcastically, then his expression changes. "Why are you here?" he asks angrily. "You know we have no business together."
"As Death Eater and Order member, perhaps. But as cousins…" My face slips into a pout. "It's been so long since we saw each other—we used to have such fun. Sirius, please!" I step toward him. "You know I've always loved you; why are you so cruel? The other Death Eaters mean nothing to me. I miss you so much. Why don't you join the Dark Lord? We could do so much together!" I take another step. "Please, Sirius."
He laughs mockingly. "Always loved me? You married that Lestrange bastard—you tortured the Longbottoms! How could I possibly have any feeling for you except hatred? And to join the Dark Lord—how could you suggest such a thing? I'd rather die!" Thunder booms loudly overhead as he says this.
And you very well might, I think. "Sirius, I'm risking my life to see you and you doubt that I love you? I'm hurt! As for Rodolphus—a mere necessity. It was a good match." I slip my wedding ring off my finger and toss it into the air. As it falls back down to Earth I blast it with my wand. "I miss what we used to have, Sirius. Don't you think we could work it out somehow? I—I'd join the—the Order, Sirius, I really would!" I cross the final distance between us and grab his shoulders. "What I've done doesn't matter anymore! All that matters is us!" I press my lips to his roughly and he kisses me back, hard. He grabs the back of my head and holds it tightly, trapping me in the kiss. With his other hand he feels his way down my back and pulls me even closer to him. Through his thin robes I can feel the muscles of his chest and stomach. I break away from him to draw breath. "Remember how we used to be? I miss that."
In answer Sirius pulls me back to him. He kisses me; I put my hands in his long hair and suck on his lower lip. He moves his lips to my neck and I wrap my legs around his muscular form. I can feel him sucking and biting the soft skin of my neck and I shiver in pleasure. When he kneels to the ground I just look him in the eyes and smile.
Sirius
When I hear Bella calling me I am surprised, but I conceal it well. I wonder why she's here, what she could possibly want from me. I am angry with her for putting both of us in danger, for risking her life to see me. Then she speaks. Now I understand her reason for coming to see me—she wants fun, like what we did as teenagers. At that time it seemed meaningless, and it feels that way now. I don't believe her claim about joining the Order; I know she enjoys evil too much. Even as children it was obvious what she would become, especially with our upbringing.
Even though I don't believe her claims, even though I hate her with the bottom of my heart, I don't resist her kiss. I can feel the pull of danger, and of excitement—long-lost sensations for me. Her taste arouses things from my past, and I know I cannot resist her—I never could.