You can imagine, Harry, that Remus and I have been over this ourselves a few times since working out the truth. Peter had been turning me, in particular, against Remus, as well, for a long time before we learned that Voldemort was coming after your parents.

I can't even be certain now whether making Peter their Secret Keeper was really my own idea or one that Peter actually planted through hints and other signals.

And when he disappeared ... I let my worst assumptions guide me, I suppose.

This is rather a morbid discussion, though, Harry. Why ask about Peter, out of all of us?