"All you need to do is unbutton your shirt." The scars of the curse would linger, even when the blood was staunched, the wounds sealed, and the continued damage ended. Severus had a very, very viscous spell in his repertoire now.

It sounded like an invitation to Sirius to bare himself, and in a way, it was. Severus grunted and got to his feet, dropping the mushroom to stalk across to the other boy. His hands moved right to his shirt. And sure enough, once his buttons were undone, there they were. Scars. Severus traced one.

"Told you."