"No," Sirius shakes his head, "no, it was. I was the one who thought you the traitor, even when James and Lily—" Sirius’ voice broke, but he continued, "when they believed you innocent. And I was the one who told James to switch secret keepers. I was the one who thought to use Peter. I handed them to Voldemort, and I didn’t betray them but it was still my fault."