One summer night, when Dumbledore arrives at Privet Drive to collect Harry Potter, his wand hand is blackened and shriveled, but he will not reveal why. Rumours and suspicion spread through the wizarding world – it feels as if even Hogwarts itself might be under threat. Harry is convinced that Malfoy bears the Dark Mark: could there be a Death Eater amongst them? He will need powerful magic and true friends as, with the help of Dumbledore, he investigates Voldemort’s darkest secrets.