The wizened headmaster stepped into the deserted girls' lavatory. No student had stepped into it since Miss Blyth's death; they were frightened.
"Miss Blyth," he said softly, "may I see you, please?"
Nothing happened, for a moment. Then the apparition appeared.
She looked exactly the same, except that she was hedging transparency.
"Professor Dumbledore." she murmured as she floated before him.
"When Mr. Black mentioned seeing you, I had a hunch that his sightings were not born out of madness."
The ghost said nothing.
"Why have you not told Mr. Black that you chose to become a ghost? Why let him believe he is merely seeing things?"
"I want to haunt him until he admits it, Professor."
"Admits what, Miss Blyth?" The headmaster questioned.
"He told you that he had no hand in this. He didn't hold the wand to my head but his hands certainly aren't clean."
The following day, Sirius Black was relaxing in the prefects' bathroom. He had coerced the password from a blushing prefect.
A feminine cough drew his attention. Hardly one to be embarrassed, Sirius lazily opened his eyes, making no attempt to cover himself.
He jumped however as his eyes adjusted.
"Myrtle!" he spluttered.