Talk to Myrtle.

"What's going on, Myrtle?" you ask uncomfortably.

"Oooohhhhhh", Myrtle yells, an ear-splitting howl that makes you cover your ears. "You'll never guess what happened to me!"

"What happened?" you ask resigned that Myrtle will tell you her tale whether you want to or not.

"I was swimming in the Black Lake this morning", she begins, "trying to drown myself, actually. Not that I can drown anyway, considering I'm already dead."

"Go on", you prompt.

"I was in the Black Lake", Myrtle repeats, "When I head this strange sound. It sounded like really loud humming."

"Loud humming?" you ask, struggling to keep disbelief from your voice.

"Yes", Myrtle replies defiantly. "It definitely sounded like humming."

"Was it coming from the Durmstrang ship?" you suggest. "It could be some sort of Durmstrang tradition."

"No", Myrtle says, certainty in her voice. "It was coming from the side of the lake opposite to the castle, near the Forbidden Forest. I flew closer to investigate, and saw some students standing around an object. The humming was coming from there."

"What was it?" you ask, interested at last.

"I don't know", Myrtle replies, shrugging. "I didn't get close enough."

You sigh in frustration. What was the point in seeing some interesting thing like that, and not investigating?