Sirius paused, knife still buried inside of Remus' stomach, a flicker of - something - in his eyes when Remus begged. He frowned very slightly, a quiet voice in the back of his head asking if he really wanted to push the knife in further or not.
Why not? Sirius reasoned, watching Remus closely, as though he'd done something unexpected. This was fun, wasn't it? This power, Remus' suffering, the experience of it all? Intoxicating. But was it? He drew his hand back slowly, uncertainly, still looking confused and a little foggy. Why was he doing this? Was it really as exciting as he'd thought? Didn't Remus seem to... not be enjoying it as much?
He blinked once, twice, three times, head feeling as foggy as he looked now, torn between wanting to continue and wanting to stop. He couldn't explain either feeling, couldn't argue for either side of the matter; he only knew he was confused. "I-" he said, but he didn't know how to continue.