If Remus wasn't in so much pain, he probably would have gotten hard from seeing Sirius kneeling before him like this. His eyes were on Sirius' face, unable to look away as his wand traced over his leg. He could feel the heat in his foot and took a deep breath, knowing this was just the beginning. The physical pain combined with Bellatrix's taunting was driving Remus mad.
"It's not really him," he gasped, finding it difficult to breathe and talk at the same time as his foot burned. It was layer upon layer of pain and Remus was really struggling to deal with it. "It's not... his choice."
He screamed as his foot blistered, his eyes screwed up tight as he winced, panting for breath. "Sirius!"