Definitely took some medical liberties with this. Also, this isn't part of my Shrapnel Hearts canon. And I didn't know what to rate it. Anyway, enjoy.
"I don't think we can deny this is happening any longer, smoothskin." Charon cupped Truth's jaw in one large, ravaged hand and studied the skin falling away from her face. With his thumb he lightly traced the snout of a nose she still had left after the tip disintegrated in the midst of a fight and then her dry, cracked lips. Her green eyes streaked and speckled with brown were narrowed in pain as she looked up at him. They hadn't yet begun to cloud over and stood out from her cracked and scabbing face with striking clarity and no less ferocity than he'd come to expect from her. Somewhere between human and ghoul, his vault dweller looked more like an animal than anything else.
Truth scowled and pulled away to feel her own face and then examine her hands that were covered with similar sores. "You're gonna have to stop calling me 'smoothskin,' then."
Charon grinned mischievously. "Not until you stop being prettier than me, I don't." He paused long enough for her to laugh and shake her head before asking, more seriously, "How're you feeling?"
"Like I'm on fire." The tension in her posture and her jaw attested to that. Ghoulification was rarely painless. Most nights, neither of them slept much because Truth tossed and turned and whimpered as she tried to ignore the burning itch long enough to fall asleep.
"It stops eventually," he assured her, "Once the top layer of skin dies."
"Yeah, but how long is that gonna take? It's been months." She retreated into her thoughts and scratched furiously. Flakes of dead skin floated away from her on the hot wind. "Barrows is gonna be pissed. We ought to stop by Underworld and let him know." They weren't more than a day's walk from the ghoul city anyway.
"If that is what you wish," the big ghoul bent to kiss the top of her head where the orange hair was already falling out in patches, "I shall follow."
Truth grabbed his collar as he pulled away and leaned in to close the space he'd put between them. "What's the matter?" she teased, "Can't stand to kiss a ghoul on the mouth?"
Charon laughed and kissed her lightly, on the mouth, noting the new roughness of her lips as they moved against his. "You'll still have a mouth," he explained, "it's your hair I'll have to miss." He ran his fingers through the thin, orange strands and tucked the flyaways behind her ear, trying not to think about how he'd have to watch that ear fall off, too.
"If you'd stop pulling on it, maybe it wouldn't fall out so quickly."
He answered her with a playful tug that won him a tuft of hair and an accusing glare from Truth. "Are we going or not?"
"Yeah, yeah," she griped, grabbing her things together. "Come along, soldier."
Doctor Barrows stared when Truth walked into the Chop Shop, Charon at her back, and stood before him sheepishly. "Well," he tsked and threw the clipboard he'd been studying onto his desk with a clatter, "There goes my supply of smooth skin."
Truth grimaced apologetically. "We hoped it was just a rash but…" she shrugged. But it'd gotten so much worse. "I thought you might want to study the transition."
The older ghoul's face lit up. "Oh, yes, that would be… very helpful!" A little stunned, he got up and retrieved a battered old folder full of yellowing pages and flipped through it. "I'm glad you thought of it. I knew there was a reason I liked you. Shall we get started? "
Charon chuckled and took Truth's pack. Once she'd climbed up on a gurney to let Barrows begin taking blood and skin samples, Charon left, briefly acknowledging Truth's parting wave. He didn't like to be around while they ran tests. She enjoyed the research but watching lent too much weight to his own memories of being tested and experimented on. So instead, he took their salvage to Tulip and bought what supplies they needed and then spent the next few hours in the Ninth Circle, cleaning their weapons and soaking up the news around town.
When he returned to the Chop Shop, the tension in the room was thick and Truth and Barrows argued over a microscope and a pile of medical books and papers. Truth wore a series of new bandages and her face was flushed with exasperation.
"You're a scientist, Truth, we're looking at the same thing..." Barrows was saying.
"You don't think that, after what I've been through, it's a little more likely I'd be turning into a ghoul? You know how many times I've had radiation poisoning?" she demanded.
"Yes, and I know how many times it's put you in a coma," Barrows sighed and insisted, "I think it's entirely more likely but that's not what's happening here."
Charon set what he was carrying down nervously and demanded, "What's going on?"
"Barrows doesn't think I'm a ghoul," Truth informed him, crossing her arms, and then said sharply to Doctor Barrows, "I don't have a nose."
"You have leprosy."
"Where would I have gotten leprosy?"
Barrows shuffled through the pages of one of his books. "It could've been anywhere, really, possibly another ghoul who really has leprosy. It is contagious, though prolonged contact would cause it to develop faster..." As he spoke, a shift in his thoughts passed visibly over his face, the same that passed discretely between the lone wanderer and her stalwart ghoul companion-turned-lover. "Charon," Barrows addressed him thoughtfully.
"I am not a leper," Charon growled. He appreciated that Truth, at least, found the accusation appalling enough to blanch.
Barrows ignored both of them, the cogs were already turning is his head. "How old are you?"
Realizing that the ghoul doctor meant to get his answers, Charon fumbled, "Fifty, maybe? I changed fifteen or so years ago."
"Would you mind—"
"No," Charon cut him off instinctively.
"Leave him alone," Truth tried, but the question was already in the air and, though he trusted her to let it be, he knew both of them would wonder. With a little more coaxing from Doctor Barrows, he let the tests be taken.
Truth leaned against him, tracing her fingers over the ruddy, uneven patches of skin on his arms while Doctor Barrows worked. Once in a while, when she became restless, she left him to help Barrows, but the rest of the time her weight was pressed comfortingly against Charon's side and he was grateful to have that if he couldn't at least have the certainty of his last decade and a half of ghouldom. They didn't speak much, both buried deep in their own thoughts.
She broke the silence once only to murmur shyly in his ear, "He's right, you know, about me. But I'd just been getting excited about us maybe being referred to as 'the dynamic ghou-o.'"
Charon groaned. "You read too many comic books."
"So does Three Dog," she reminded him and insisted it would have happened.
When Barrows finished his work and addressed them again, the couple's separate hearts sank in unison at the look on his face. "Charon has leprosy," he announced, "So that answers the question of how Truth got it."
Charon kept his face tightly blank at the confirmation. It was bad enough that Truth had to go through the pain of isolation of becoming a ghoul, learning that her predicament was his fault put a sharp knot in his stomach. He always knew letting himself get close to her could only end badly and he couldn't help thinking that giving her leprosy had to violate his contract.
"You didn't know," Truth said later, after Barrows finished telling them that they'd lost any way to treat leprosy in the war and that they were, basically, on their own. She reached across the table at Carol's to take his hands in hers. "And you couldn't've done anything about it. We're not ghouls, and we're not smoothskins, and we'll probably have to go start a leper colony," she squeezed his hands tightly, "but we've got each other. …Right?"
Her eyes were full of disconcerted sadness and pain but through that and through this new revelation she still looked at him, to his amazement, with the same affection and hope. To think he might ever not have her back or that she might ever not have his heart was preposterous. Charon managed a smile to assure her and squeezed back. "Right."