Note: For those who are unfamiliar with the symptoms of Parkinson's disease, the first and most telling sign tends to be a tremor.
He cannot hide it anymore.
Rather than continue to stare down the traitorous tremor, he closes his hand around a teacup instead, grounding himself against the cool marble countertop.
His body goes from cold to hot as volcanic anger suddenly plumes from the depths of his chest, and he lets that emotion run its course. He sucks in deep, gasping breaths, attempting to retain some semblance of control, and hopes desperately that if he is shaking now, it is from fury, not disease.
When it is over, the teacup is in splinters. Klaus begins to clean up the mess, careful not to cut himself. When he finishes, he thinks of his wife, and wonders how much time they have left.
She doesn't seem to notice for weeks. In that time, though, he is tense, prone to snapping - something he hasn't done at her in years. He hates himself for it, that he has injected their remaining time together with poison.
But he cannot bring himself to say the words.
One night, they are preparing for bed when the world suddenly seems to tilt. He collapses onto their bed with a grunt, and Clara comes running.
"Darling," she murmurs. "Darling…"
He mutters that he is alright, that it has passed. And when he looks up at her to see how she responds, he is able to read her expression as he has for years and years, since the first day he saw her, standing small and startled in a great hall in front of a scale that would decide her destiny.
She knows. Of course she does. In all their years together, she is the only one who has ever known him. Why should this be any different?
"There's no cure," he says quietly. "It'll just get worse and worse. Soon I won't be able to take care of myself, and you'll be stuck nursing an invalid who can barely get himself out of bed." That last thought disgusts him, that he who had always prided himself in his achievements, should be reduced to this - a burden, that she would have to bear alone.
He looks down, defeated, and she draws him close.
"I promised I'd love you forever," she says, "even when you turned old and gray."
The words from long ago still bring a smile to his face. "It looks like I'm putting you to the test now, Bunnyhead. You'd better not have been lying."
She kisses his forehead affectionately. "This is one test I won't fail."
That night, she disappears.
He remembers the first time they slept together, curled up against each other in bed under a tableau of stars. As serious about her as he'd been, he'd still wondered how he'd ever get used to all her little fidgets and twitches that jostled him awake.
Now her absence is what wakes him. He opens his eyes and the space beside him is cold.
He waits.
In the morning she returns. He feels the hum of her teleportation spell in the living room, and he manages to stand, cursing the trembling in his leg. She enters their bedroom and stops short at the sight of him.
"Where did you go?" he asks. There is no suspicion in his voice - only curiosity.
"Back to school."
He moves towards her carefully, teeth gritted with determination - with the conviction that no disease could take from him the pleasure of greeting his wife. She waits and allows him to come to her before tucking herself against him, arms wrapping around his waist.
There is something cool against her neck, and it presses hard against him. Distracted, he only has a moment to notice it - small, and pearly, and white - before it begins to glow.
"Clara," he murmurs. "What - "
And then his body begins to hum. It is as if youth is returning to his limbs; they are lighter, stronger than they've been in months. He closes his eyes against the flow of holy power, squeezing his arms around her, clinging tightly as if afraid she'll be swept away.
When he opens his eyes, he feels like a new man. He raises one hand to his face, and is stunned.
Stillness. Blessed, blessed stillness. And - he makes a fist, clenching tight - strength.
Clara is smiling up at him, through a sheen of tears.
He grabs her chin, reveling in the renewed vigor in his fingertips, even as his heart fills with cold dread. "Clara," he gasps. "How - "
"The unicorn," she says, simply.
He knows there must be more. His voice grows ragged with fear. "What price did you have to pay for this?"
She chuckles. "It's alright Klaus. I saved his life once, you know. I was able to bargain a little."
"Tell me."
She strokes his face, and her fingers move back to trail through silvery-blonde locks. "He promised, that as long as we both lived, we would be together. And that's all that matters."
Her lifespan. Whatever she might have had after he was gone, she had given up.
"Clara," he breathes in horror.
She quells his protest with a tender kiss. "Hush…"
"You shouldn't have," he murmured. "Little fool…"
Her eyes are shining, utterly serenely, like a spring under a quiet moon. "You're getting slow in your old age, Klaus," she teases.
"Why you little…"
She giggles at his empty threat, and then tucks herself back against his chest.
"Don't you see? It was a fair price for the unicorn. They live alone, and they'd never understand." She reached up to kiss him. And through her kisses, she whispered, "For me, it's the greatest gift. Now I know I'll never have to live a day without you."