Harry's Detention with Gilderoy Lockhart and Hearing a Mysterious Voice

During Harry's detention with Gilderoy Lockhart, where he helps answer fan mail, Harry hears a mysterious, chilling voice. Lockhart does not hear the voice, leaving Harry confused and unsettled. The voice, which no one else can hear, seems to threaten violence, but Lockhart dismisses Harry's concerns, believing Harry is simply tired.