While waiting for the right time to recapture Dumbledore, Amelia called the unspeakable Steven Secret into her office.
"Steven, " said Amelia seriously, "I need you to come with me to Hogwarts."
"What's up?" inquired Steven.
"I have a suspicion, " explained Amelia, "Ever since you destroyed the diary Horcrux, I've been thinking about where the other Horcruxes might be. I know that Voldemort would have kept them hidden and I know part of his strategy would have been to keep all of them in separate locations with those locations being reasonably spread apart. You know about the Room of Requirement I presume?"
"Yes, " confirmed Steven, "Ohhh. I know what you're on about. One of the things that Room of Requirement can do is become the Room of Hidden Things. You suspect Voldemort may have hidden a Horcrux in the Room of Hidden Things. "
"Yes, " said Amelia in a businesslike voice, "And given his arrogance and pride, it wouldn't surprise me if Voldemort found the Room of Requirement, including its ability to become the Room of Hidden Things, and then believed or even assumed he would be the only one who could ever find it."
"That makes all the sense in the world, " agreed Steven.
"Take my right arm, " Amelia told Steven, "I'm going to take us the area just outside the Room of Requirement via Side Along Apparition. I know you know how to Apparate on your own, but I want to make sure we arrive at the exact same nanosecond."
Steven did aa he was told and grabbed Amelia's right arm and she apparated them to the area just outside the Room of Requirement.
"Become the Room of Hidden Things but with complete silence and only us allowed in, " Amelia thought to herself three times.
Sure enough, the Room of Hidden Things appeared and once they were inside it was absolutely quiet.
"Steven, " said Amelia clearly, "I want you to search this room and listen closely for any sound of that heartbeat you heard from the diary. "
Amelia then fell silent and Steven started to walk around the room slowly and carefully, listening for that dreaded heartbeat.
This process took a very long time. How long, neither of them knew. Steven slowly walked around the room from front to back listening as intently as he could every nanosecond.
He passed various objects that could plausibly have belonged to Hogwarts students and that they could have plausibly wanted to hide: books on dark magic, banned Love Potions, objects that no doubt were being hidden from Filch, posters and magazines talking about or depicting terrible vices such as sex and sexuality, and even some cheat sheets undoubtedly being hidden from teachers and staff.
For the longest time it almost felt like a lost cause. Steven went on and on and heard nothing. But as he reached the very back of the Room of Hidden Things, he heard that dreaded heartbeat.
Listening closely, Steven could hear that the terrifying sound was actually coming from a diadem.
"AMELIA! I'VE FOUND ONE AT THE BACK OF THE ROOM!" screamed Steven.
Amelia zoomed to the back of the room faster than a cheetah chasing its prey.
Steven picked up the diadem and showed it to Amelia.
Now listening very carefully herself, Amelia could hear that horrible heartbeat. And then she was struck with a sudden pang of sadness.
"This, " realized Amelia, "Is the Lost Diadem of Ravenclaw."
"Of course, " it now dawned on Steven, "Voldemort would have wanted to use objects of significance for his horcruxes. No way he'd use an empty Skittles bag or something like that."
"I'm heartbroken, " confessed Amelia, "We've just uncovered an artifact of one of the greatest witches of all time, one of the Hogwarts founders, an object that has become almost mythical over time and now that we've found it we have no choice to destroy it."
""We've got to do what we've got to do, " replied Steven mechanically.
Locked in the room by themselves with no threat of others getting in, Amelia asked out loud three times "Give us a safe way to destroy the diadem horcrux,."
A small bowl of Fiendfyre appeared on a table in the middle of the room. The fire was clearly contained to the bowl and showed no sign of spreading.
Steven calmly walked over to the bowl and dripped the diadem in. The diadem was soon charred black and collapsed into nothing. The nanosecond the horcrux was gone, the fire extinguished itself.
"The Room of Requirement can always give you EXACTLY what you want, " smiled Amelia, "By asking for a way to destroy the horcrux, it gave us the Fiendfyre. By adding the word safe, I ensured the fire would be contained and safe to use."
"And extinguish itself after it did its job so it could do nothing more, " added Steven.
"Yep, " said Amelia.
When they got back to the Ministry again, Steven and Amelia were surprised it was only 10:30 A.M. Though it felt like much longer, it had only taken a couple of hours.
Amelia wrote to Heather to tell her about the Horcrux that was the Lost Diadem of Ravenclaw being destroyed and Heather passed the news on to Harry, Amy, Susan, and Hannah.
"We're going to have Voldemort right where we want him if he ever does manage to come back, " declared Harry.