Draco Malfoy and Severus Snape both share the same responsibility of keeping Lord Voldemort's heir--Ivory Devereaux safe at Hogwarts, and aid her with her task. Ivory is a spy for the dark side and Snape for the good. What they both dont expect is of course thrown their way. Draco, Severus and Ivory must deal with them with panache. They aren't the Dark Lord's most trusted servants for nothing.