Nathaniel has been asking around school about a strange sound he has heard on separate occasions in the Foggy Mere. In a particular spot he hears what sounds like some kind of giant insect skittering about. During one outing, he thought he bumped into something invisible, however he was unable to see anything there even aided by [True Seeing].

He has been directed to see Hagrid about it.

// Need a little help with Hagrid's answer.