Question: In the Astronomy tower, Dumbledore tells Harry to go and get Professor Snape, but then Harry has to hide. So, how did Snape know that Draco and the Death Eaters were in the Astronomy tower with Dumbledore? Draco would not have told him because he did not want help with the mission.
Greg Dwyer
9th Aug 2015
Answer: Snape was acting as a double agent for Voldemort. He knew because the Death Eaters who invaded told him.
Greg Dwyer