The switch had been Sirius' idea, of course, and he insisted on talking to Peter himself. Just as he had expected, Peter had been doubtful at first, hesitant almost, in a way that reminded Sirius of the school boys they had all been not long ago. But Sirius had been persuasive as ever, and now he sat in the Potter's house, watching as James and Lily and Peter worked the Fidelius Charm. Light flared in the semi-darkness, catching Peter's face in an odd, hungry expression, and for a moment Sirius had a horrible thought. What if this was a mistake? What if he had been the one meant to be the Secret-Keeper, not Peter? The light faded to a dull glow, and there were spoken words and the whisper of old, deep magic as the spell was completed. Sirius pushed the sudden worry to the back of his mind as the lights returned. In the safe, solid glow, the world returned to being safe and solid as well. Lily vanished upstairs with Harry, James tinkered with the Wireless, trying to catch a Quidditch match, and no one paid any mind to Peter quietly slipping out the back door.