Back at Grimmauld Place, we were favoured by a visit from Snape. Given that he and Sirius Black are less fond of each other than Harry and I are of Draco Malfoy, this was rather a surprise. I wasn't invited to the conversation, but found out later that Dumbledore had decided that Harry needed to learn Occlumency---the power to shield his mind from outside interference. And his brilliant plan was that Harry should be taught by Snape!