Narcissa Malfoy visits Severus Snape in his house on Spinner's End, accompanied by her sister Bellatrix. She resists Bellatrix's attempts to persuade her not to trust Snape, and is determined to talk to him. Narcissa tells Snape that he is the only one who can help her, and that she has been told to say nothing to anyone by Lord Voldemort. She is reprimanded by Snape for attempting to disobey Voldemort, but is thankful when the Professor reveals he knows about the plan already. Narcissa tells Snape that she is worried about the task Voldemort has set for her son Draco, and is certain he was chosen as revenge against her husband, Lucius, for being captured and failing to retrieve the prophecy from the Department of Mysteries. She is certain Draco will not succeed, and begs Snape to persuade the Dark Lord to pardon Draco from the task. She sobs as Snape admits it is unlikely Draco will succeed, crumpling at his feet and crying on the floor.
Narcissa asks Snape to make the Unbreakable Vow to help Draco as he attempts the task. She kneels on the floor opposite Snape, clasping his right hand with her own as Bellatrix performs the spell. She asks Snape to watch over Draco as he attempts to fulfill Lord Voldemort's wishes, to protect him from harm to the best of his ability and to carry out Lord Voldemort's task if Draco is unable to, or appears to be failing.