The Dark Lord sent me to complete a task for him while he’s away from Malfoy Manor. He had me retrieve a relic from the Room of Requirement at Hogwarts; Ravenclaw’s Diadem. I believe it to be one of his Horcruxes. At present, it is located in the Malfoy’s Treasury, a room that is only accessible through a secret entrance in Mr. Malfoy’s study. I presume Dobby knows where that is.