Jon watched Professor Galatea Merrythought's face and asked, carefully sincere, "A way to resolve it?"
"The cure?" The old witch sighed, then shook her head. "To be frank, it is very difficult if it cannot be broken. Unless I remain in this post for good, or die and leave this world, this curse will not stop."
It was the answer he had expected. Jon fell briefly silent. After a moment, he asked, very quietly, "If the caster, I mean hypothetically, if He-Who-Must-Not-Be-Named vanished from the world entirely, would the curse vanish with him?"
"Are you joking?" Professor Merrythought gave him a strange look, as if startled that he could err on something so basic. Her voice turned slightly sharp. "You do not imagine a curse is like those Muggle tales describe. This is a curse already cast, magic already performed. It no longer depends on him."
Jon managed a faint, abashed smile. "Apologies. I am still too young. There are gaps in my foundations. I've given you cause to laugh."
It was not false modesty. His time in the wizarding world had been short; he had learned from many remarkable teachers, but his base was, overall, ordinary.
"I almost forgot, you are not yet seventeen," the old witch said, and her tone softened.
"Of course, there is another matter," she went on. "Why He-Who-Must-Not-Be-Named could make use of this arrangement at all."
Jon did not interrupt. He listened.
"Choosing me as the target was, honestly, very clever, even brilliant," she said, weighing each word. "He was my student for years. He knew me quite well, which lowers the difficulty of the curse. And not long after he cast it, I resigned from Hogwarts. For many years after, I kept little contact with the wizarding world."
"So," Jon nodded slightly, "Professor Albus Dumbledore was a truly great wizard, but even he had no way to address Tom's curse. He could not access the target of the curse and had nothing solid to judge."
"Yes." Merrythought's sigh carried a thread of grief and fondness. "If Albus were still alive, still at Hogwarts, with his insight he might have spotted the curse on me in a few days."
"Then, to the point, Professor," Jon said, gently cutting across the sadness. "What exactly did you mean by your question?"
"There is nothing strange about him cursing me; his power long ago surpassed mine," Professor Merrythought said slowly. "But the content of the curse, that I could never leave the post of Professor of Defence Against the Dark Arts at Hogwarts, that puzzles me."
"Hogwarts is a magical construct with a strong will. Even he would find it hard to fool it with a Confundus Charm, and he should not have that kind of authority. Only the Headmaster can do such a thing."
"Wait." Jon's face changed.
He thought for a beat, then said, more formal now, "If we are speaking of Headmasters, Tom could not have struck a bargain with any of them. Except, perhaps… our very first Headmaster."
"Salazar Slytherin?" Professor Merrythought asked, nonplussed. "He has been dead nearly a thousand years."
"Quite right," Jon said. "But before he left Hogwarts, Salazar Slytherin left something in the castle."
"You mean the Chamber…" Even Galatea Merrythought, for all her age and strength, lifted a hand to her mouth. "I remember, long ago, the Chamber of Secrets was opened."
"Tom Riddle was at school then, was he not?" Jon smiled.
A voice from the wall, ill-timed as ever, broke in. Armando Dippet's portrait poked out its head and murmured, "Sounds as if you're discussing my black marks."
Jon and Professor Merrythought did not oblige him.
"Without question," Jon continued, "Tom Riddle, He-Who-Must-Not-Be-Named, is Slytherin's descendant. In the Chamber he may have come into contact with a portion of his ancestor's, let us call it, legacy."
"And without question, Professor Dumbledore played a critical role." Jon glanced sidelong at Dippet's portrait. "While the Headmaster of the day noticed nothing, he detected the change in Tom Riddle. From then on, while still at school, poor Tom could no longer open the Chamber."
"That is likely why Tom always wished to return to teach at Hogwarts," Jon went on. "Fortunately, Professor Dumbledore refused his application."
"When Dumbledore turned him down, he was already a very powerful Dark wizard, perhaps a shade below Dumbledore. I suspect he went down to the Chamber once more, then, upon the Defence professor who was about to retire, cast this curse."
"A neat analysis," Professor Merrythought said, giving a small, appreciative clap. "But, regrettably, only Slytherin's heirs can enter the Chamber. We are powerless against this curse."
"I do not think that is any great loss," Jon said with a faint, secretive smile. "At least the truth is plain now. Until this curse is entirely lifted, I must ask you to remain at Hogwarts as Professor of Defence Against the Dark Arts. Otherwise, we will invite another victim."
The old witch hesitated. After half a minute, she ventured, "Then my salary is doubled? Prices have been dreadful of late."
"Done," Jon said without a moment's pause.