A Christmas party was hosted by Professor Horace Slughorn on the evening of 20 December, 1996 in his office in Hogwarts School of Witchcraft and Wizardry for his favourite students, the Slug Club and their dates, as well as former club members and various other associates. Harry Potter, Slughorn's most welcomed guest, overheard a strange conversation between Professor Severus Snape and student Draco Malfoy during the party that made him suspect that they were conspiring on behalf of Lord Voldemort.