Harry sneaks off from Slughorn’s Christmas party to follow Snape and Draco, and overhears them having an argument about Draco’s mission.
Harry becomes suspicious, but he doesn’t learn that Draco is tasked with killing Dumbledore.
Harry eavesdrops on Snape and Malfoy
Date circa December 20, 1996
Location in Canon HBP15
Type of Event Wizarding world