This is a oneshot that came to me from thinking two thoughts. The first was, of course, "What would happen if Harry had been holding back his feelings for Hermione since fourth year, but hit his limit around the time Ron and Hermione made out on the way to the ROR in the Battle of Hogwarts?" The second thought was, "How many magical diseases are there in the Wizarding World?" After listening to one specific song, this came to mind. There will be a part II that will close the situation up, but so far, here it is.
In this case, Voldemort gives the one-hour reprieve earlier than in the book, so Harry has not yet seen the memories of Snape, who is still alive.
Song that came to mind is by Daddy Yankee, called "Llamada de Emergencia". If you know Spanish, give it a listen if you haven't already.
"Madam Pomfrey!"
The loud yell startled everyone inside the destroyed Great Hall. As one, the survivors of the first assault on Hogwarts turned to the source of the yell and saw Hermione Granger and Ron Weasley running into the Hall, and behind them, the floating, writhing form of Harry Potter.
"What's the matter? What's happened?" Pomfrey said in a no-funny-business tone. This slight reprieve from the Death Eater assault that Voldemort had granted the Hogwarts defenders was filled with tension and grief, as families were now allowed to mourn the dead temporarily, and those who weren't dead yet had poor Pomfrey running back and forth continuously.
"I... I don't know," Hermione admitted, bringing Harry to the ground in front of her and releasing the body bind she had kept him in, at which point Harry curled himself into a ball and grabbed at his chest, clawing at it as if his lungs were burning. His mouth was open and contorted, meaning that if it weren't for the silencing spell on him, he'd be screaming loud enough to wake the oldest forgotten gods. "We were headed to the Room of Requirement-,"
"Where?" Poppy asked, already waving her wand over the seventeen-year-old, her face slowly becoming paler.
"It's a magical room on the seventh floor that becomes whatever the user wishes for, like chamber pots if you really needed to go," Hermione explained hurriedly, wincing a little at the description she used. Most of the survivors had already gathered around them. "Anyways, we were headed there because Harry explained that one of the key objects to defeating Voldemort was in there, but on the fifth floor, where Ron and I met up with him, he suddenly collapsed and started doing this!" She pointed at the convulsing Harry, fear in her face. "Madam, please, what's the matter with him?!"
She had barely noticed the fact that Ron had left her side, more preoccupied with Harry's health than anything else. He hadn't come in contact with anything that should have caused him to react like that.
Poppy finally stopped her examination of Harry and studied him with a critical eye for a moment before summoning a Dreamless Sleep Potion from her supplies and coaxing it down Harry's throat. It took a few moments, but eventually, Harry calmed down and entered a fitful rest, his face still contorted in pain. Absently, Hermione cancelled the silencing spell, and watched with trepidation as Pomfrey took off her spectacles and rubbed her eyes (whether in tiredness or frustration, Hermione couldn't tell) muttering something along the lines of, "why would this happen now?"
"Madam Pomfrey, please, tell me what's wrong," Hermione pleaded with the matron, the other Hogwarts defenders sharing the same plea with their eyes.
Poppy finally looked up and asked an open question, although she was looking directly at Hermione. "Have you ever heard the phrase 'dying from heartbreak'?"
Many of the students around the women, most of them pureblood, gasped in shock, while the rest, Hermione included, only stared at the woman in confusion.
"Madam Pomfrey, you think Harry is dying of heartbreak?" Hermione asked in a disbelieving tone.
"I don't think so, miss Granger. I know so," the matron replied sternly, showing that she was not joking in the slightest. "While dying of depression due to heartbreak is a rare occurrence in the muggle world, it is prevalent and much more fatal for wizards and witches."
"You must be kidding me," Hermione said.
"I assure you, I am not. Mr Potter... Harry's..." Poppy's eyes teared up slightly as she looked at the fitfully resting boy she had treated for six years. "He's truly dying of heartbreak, and by my estimates... He only has about an hour before it... claims his life."
Gasps rang out around her, the loudest coming from Hermione.
"No... no, that can't be! Why now?! Why would it happen to him now?! And how does it even happen?"
The matron sighed as she explained. "Cor contritum morbus, as we call it, is a rare but fatal disease that could strike anyone. It happens whenever the person in question forms an extreme emotional attachment to another living person, either magical or muggle, even if they do not realise it. When something happens to the one they have attached themselves to, say, for example, they are betrayed by him or her, or their feelings are unrequited, the pain of loss, denial, or betrayal can be strong enough to turn their own magic against them, attacking their own body. As I said, it's rare, but when it strikes, it is most definitely fatal."
Hermione slumped to the floor after the explanation, staring at the contorted face of her best friend. After all they had gone through in their time, the thing that would do him in was heartbreak?
"As to why the curse became active now, I cannot say. By my estimates, he has had it for some time already, but managed to keep it in check somewhat. That only seemed to worsen the curse, however, and whatever caused him to let it attack him must have been something akin to the 'last straw' for him." Taking a breath, Poppy looked at Harry with wet eyes. She had treated a fair number of patients with a similar disease, and almost every single one died some time after they had acquired it, though none as quickly as Harry.
"Is... Is there a way to cure him?" Hermione asked meekly, grabbing Harry's hand and squeezing it.
Poppy nodded, noticing as one who has been a healer for a long time would how Harry's face relaxed, just slightly, at the contact with Hermione. "There is, but it is extremely difficult, especially in this situation."
"How?!" Hermione asked desperately.
"The only way to cure it is for the one that caused the heartbreak to push his or her magic towards Harry. This can only work, however, if the person who Harry is in love with reciprocates those feelings. It can be familial, friendly, or romantic love, but it has to be reciprocated, else we run the risk of accelerating Harry's death. And no, miss Granger," Poppy was quick to say, noticing Hermione open her mouth to ask a question, "No one other than the person responsible for the heartbreak can cure him. And unfortunately, we have no idea who is the person that caused it. The only one that could tell us is Harry, and he is in no condition to do so."
"Oh, Harry..." Hermione moaned, holding on to his hand tightly. "Who is it that's hurt you so much?"
Harry, of course, didn't respond. Trying fruitlessly to keep her head from the thoughts of her best friend's death, Hermione looked around and tried to find Ron, locating him some yards away with his family. Squeezing Harry's hand once, she stood and made her way over to him, noticing halfway there that they were actually mourning Fred.
Tears welled up in her eyes at the thought of the fun-loving Weasley twin, but she continued towards her probably-boyfriend and put a hand on his shoulder. He didn't respond.
"Ron?" She tried, moving forward and hugging his side. "I'm so sorry..."
Together, Ron and Hermione silently mourned his brother, watching with wet eyes as Molly wailed and hugged her son's body.
Some minutes later, it was Ron who broke the silence between the two. "How's... Harry?"
Hermione wasn't prepared for the onslaught of emotions that would come from that simple question, but she finally focused on the news she had received earlier and her crying doubled. "Not well. Have you ever heard of cor contritum morbus?"
Ron stiffened at the mention of the curse, leading Hermione to believe that he did indeed knew. "But... I thought that was just a myth... a children's myth..."
Hermione sighed and laid her head on Ron's shoulder. "Apparently not. Madam Pomfrey says Harry's had it for a while now, and it only now triggered. He's bad. Really bad, Ron. He only... only had a-an hour t-to live when w-w-we brought him in..." Hermione's crying began anew, making it hard for her to finish.
Ron's face became even more grief-stricken at the news, and he looked back towards where Harry was laying down, surrounded by his friends and comrades.
"I've already lost Fred..." He moaned. "I can't lose one of my best friends too..."
"I know, Ron," Hermione said into his shoulder, her voice thick with emotion. "I feel the same. But what can we do? It's clear something's been hurting Harry emotionally for a while, enough to cause him... this. And without knowing who his feelings are for, there's no way to heal him..."
To her surprise, Ron actually became thoughtful at that piece of information, but if he was thinking anything, he didn't voice it.
The Hogwarts defenders remained so for a long time, many keeping track of time. Time seemed to fly, and in what seemed to be only a few minutes, Hermione was aware of someone shouting loudly that they only had five minutes until Voldemort's hourly reprieve ended and he would attack again.
Everyone stood with bated breath, waiting to see what would happen. The minutes counted down, the seconds ticked away...
And the hour came with a rather strong greeting.
Almost as soon as the second hand marked the start of a new hour, a loud, pain-filled scream rent the tense air, making many in the Great Hall startle. Hermione, Ron, and Poppy were the first to lock onto the origin of the sound, the former two because they had been looking that way periodically, and the latter because she had put wards around the area that alerted her of any trouble.
Harry's eyes had suddenly snapped open, and a second later, he began screaming in pain, his muscles cramping as he clawed at his chest and gripped the sheet he was lying on with a death grip. His screams unnerved everyone. They were filled with pain, anger, sadness, and a million other emotions, which only increased as time went on.
"Harry!" Hermione and Ron yelled together, running towards their best friend. Everyone was still in shock, so they were able to reach him safely unperturbed. Hermione immediately tried to grip his hand as she normally did, but was violently rebuffed when Harry's hand jerked away, nearly throwing her onto him.
"Harry! Please, fight it! You can fight it!" Hermione cried in desperation, trying to reach Harry but finding herself held back. She looked back and noticed Ron holding onto her arm, looking at her with a morose expression. "Ron, let me go! Harry needs my help!"
Ron merely shook his head and pulled her to him, hugging her and keeping her there. Hermione tried to protest, but knew that there was nothing she could do, only watch as her best friend was ripped apart by the disease that had latched onto his magic. Behind them, Molly was once again wailing at the inevitable death of a boy she'd come to know as a son, while Arthur merely held her, his face wet with a large amount of tears.
As Harry's screams reached a crescendo, a bright light suddenly materialised over his body like an aura, shining brighter and brighter until it nearly blinded people. A darker light appeared over his scar, twisting and turning like a snake in pain. As the light almost became unbearable, the dark energy erupted from Harry and formed a large funnel above him, whereupon an inhuman shriek rang out in the Great Hall. Many of the younger defenders screamed in fear, but thankfully, the shriek didn't last very long, and the dark cloud dissipated into thin air.
Harry's screams brought everyone's eyes back down to the shining man, whose back was now arched and whose hands were tight enough to draw blood from his palms. His eyes suddenly snapped open once again, this time glowing with the same ethereal light that his body had, before suddenly, the bright aura around him shattered as if it were made of glass, his eyes closed, and his body fell limply onto the blanket.
Silence reigned. The darkness that had been held at bay by the light emanating from Harry covered them all once again.
Hermione, eyes wide and mouth slightly open, slid out of Ron's embrace and shuffled over to Harry's limp form. No one tried to stop her. She knelt down at his side, looking at his now calm face, and placed a hand on his shoulder, shaking it a little. "Harry?" She said, in a tone of voice that had many looking away in sadness. She sounded lost, like a small child trying to talk to a deceased parent. Her shaking became slightly more frantic. "Harry, please, wake up. Harry… Come on, Harry. We need you. I need you. Please, Harry! Please, wake up!"
The bushy-haired Gryffindor was now shaking Harry very hard, trying to wake him up. In desperation, she looked back and locked eyes with Madam Pomfrey, who was crying just as hard. As much for her sake as for the girl's, Poppy pulled out her wand and swished it over Harry's body. Nothing happened, and Poppy's voice made everyone gasp.
"He's gone."
Hermione's eyes widened as she turned back to Harry's body. She couldn't come to grasp with it. How could this happen? Her Harry was strong, humble, kind… how could someone hurt him so much that they'd cause him to die?!
Without any other thought left, she promptly threw herself onto Harry and did the only thing left inside her: she cried. She cried for her best friend, for his terrible life, for all he had to endure in his short life. She cried and cried, and soon many others joined her, kneeling by the seventeen-year-old and crying just as hard. Hermione could barely notice Luna, Ginny, Molly, Ron, George, Neville, Katie, Angelina, Alicia, and many, many others kneeling by her and crying. How could they not? Their saviour, their Golden Boy, but most importantly, their friend, was now… gone.