Sirius Black sat in his old bedroom in Number 12, Grimmauld Place the evening Harry and his friends had returned to Hogwarts after the Christmas Break. His mood fit the dark room with its fading crimson wallpaper and musty smell of long disuse. He stared unblinkingly at an old photo that featured four of the best friends that had ever crossed the threshold of Hogwarts School of Witchcraft and Wizardry.
That is, they were four of the best friends. Now they were down to two. Sirius had a sinking feeling in his stomach as he remembered the day he had let James convince him that they should include bumbling little Peter Pettigrew in on their discussion about how best to get back at Filch for putting them in detention their second weekend at Hogwarts. Sirius had finally relented when James had said sympathetically, "He's just sitting there, like Billy-no-mates!" If only he'd stood his ground then… none of this would have happened.
But he'd made other mistakes over the years. Despite his initial reluctance in letting Peter into their trio, he'd actually grown to trust the bloody rat, inviting him in on secrets; helping him become an Animagus.
That trust was the true beginning of the end. Simply letting him in on their little gang wouldn't have caused the same trouble that trusting him did. Sirius never gave Peter enough credit – he typically appeared so gormless that when a traitor was suspected within the Order, Peter was the last person they'd expected. They turned instead to the obvious – the clever one with the dark connection.
In an attempt to avoid the obvious, Sirius had made what was perhaps the most critical mistake. He convinced James to use Peter. Pathetic Peter Pettigrew, so meek and foolish that no one would suspect he was the one trusted with the most important secret. Sirius put his head in his hands as he recalled James' reluctance to use Peter, "But you would be so much harder to break!" James had said worriedly. Sirius had insisted that no one would even suspect Peter, so the ability to withstand interrogation wouldn't be necessary.
At least Sirius had been right on one point. There never was any interrogation.
But then not fighting for Harry… and allowing Peter to escape… the days after James' death were plagued with mistakes. And then finally allowing Peter to escape a second time a year and a half ago. It was a long, poorly woven thread of mistakes that lost him first his best friend and then his freedom.
