The heat had lingered all day, reflecting off the cobbles, the walls and the roof tiles. Now, as the sun lowered behind the rows of timbered buildings, the air felt heavier, turning the narrow lanes near the Neumarkt sluggish and lethargic. Long and warped shadows stretched across the cobblestones like the city itself was beginning to sag under the weight of the summer.

  Vendors were folding up their stalls. A pair of boys wrestled over a half-eaten apple. Somewhere behind a leather shop, a dog barked at nothing and kept barking. The bells from St. Thomas’ rang out prominently, a slow call for vespers that seemed to take longer than usual to fade.

  Thomas walked steadily down the sloping street towards the square near St. Lawrence’s Chapel, his boots dusted from the walk, his collar still damp from the basin. He was dressed plainly, but the linen was fresh and his beard was trimmed. A small parcel wrapped in waxed cloth hung at his side. It contained a finger-length of smoked herring and a few soft figs from an old woman’s garden – a patient who claimed that fruit cooled the heart. In this summer heat, Thomas was liable to agree.

  He paused just before the square, waiting for a cart to pass. A fiddle played somewhere to his left. He wouldn’t exactly call it music. It was almost melodic, but not quite. A few stray beats made it feel awkward and uneven. He adjusted his grip on the parcel and stepped forward into the crowd.

  The market hadn’t emptied yet. The last of the bread sellers were shouting out their reduced prices, trying to offload the staler loaves. Some older gentlemen were sitting in the shade, enjoying their last mug of beer.

  Thomas scanned the edge of the square. Gretchen wasn’t there. At least, he hadn’t seen her yet. But the crowd was conspicuously thick in one spot, just to the right of the old water trough. The sound that emanated from there wasn’t just conversation. There were other sounds mixed in, and it was hard to tell what they were. There was an unusual rhythm to them. Repetition. Something seemed not quite in control.

  He frowned and pushed through the crowd, hand clutching the parcel carefully. It was more out of curiosity than anything else.

  At first, Thomas could only see the backs of shoulders – townsfolk packed too tightly around the centre of the square, murmuring with that peculiar hush that falls over a crowd when they don’t know whether to be amused or afraid. Elbows jutted out. A child was the loudest person there. He was clearly amused and confused at the same time.

  The smell hit Thomas first. It was something raw and sour beneath the usual tang of sweat and baked stone. He heard a man say, “There’s another one,” followed by the distinct thump of feet slapping the cobbles with an irregular rhythm too quick for any reel or dance he knew.

  He stepped between two fishmongers and saw it. It was an eerie spectacle, intriguing and frightening at the same time.

  Four figures moved erratically inside the widening circle. The light, now a brilliant golden hue from the evening sun, caught their clothes in flashes, reflecting off sweat-soaked shoulders and tangled hair.

  The rightmost figure from Thomas’ perspective was an older man. His trousers looked as if they were covered in flour, maybe he worked at the mills. He jerked with spasms so sudden it seemed as though his spine was being yanked around on a string. He danced with his teeth bared, the corners of his mouth cracked and bleeding. His knees bent, then straightened too fast, as if his limbs were rebelling against the rest of him.

  This old man was the loudest of the four, and thus the one that Thomas and anyone new to the spectacle would notice first. He was talking while moving. It was not very coherent, but it was fast and highly energetic. He seemed to be complaining about something.

  Another participant was a plump woman in her thirties. She spun with her hands clasped tightly to her chest. Her apron slapped against her thighs with every turn, and the hem of her skirt had torn loose and trailed behind her like a ragged tail. Her hair had come loose and was now whipping against her sweaty neck.

  Then there was a boy, no older than fifteen. He stumbled repeatedly on bare feet that were already bruised. He blinked quickly, as if warding off tears or maybe just the light. Then he flung his arms upward, looking like he was about to jump. But he didn’t. Instead, he landed harder, as if gravity had changed its mind mid-motion. There was something in his expression that suggested a futile attempt to stop doing whatever he was doing.

  And then there was… Gretchen.

  Thomas froze when he saw her, his breath catching between his chest and throat. He was horrified. He had been hearing about this strange affliction and had given it superficial consideration. He knew he did not have a clear answer to it. But here was fate dragging him firmly into this mystery. There was no time to prepare and no way out of it.

  Gretchen was near the centre, her back to him at first. Her braid had come loose and now hung like a rope down one side of her neck. The rest of her hair was tangled and soaked in sweat. She wore a dress made of blue-grey cotton that Thomas recognised. But the sweat darkened it now. One side was smeared with something that looked like wet rye. Her apron, which she’d always kept perfectly knotted, hung askew, the strings snapped. Her feet were bare. Red patches showed across her heels and the balls of her feet – blood, definitely blood. Yet she danced as if she couldn’t feel it.

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  Her body moved in quick, erratic pulses, not in sync with anything obvious. Her arms stayed close to her sides for a moment, rigid, then flared outward suddenly like she was shaking something off. Her head snapped once to the right – again – then again – and then she spun fully in a tight, staggering circle.

  Her eyes passed over the crowd once, wide and empty. Then they locked on him.

  For one terrifying second, Thomas wasn’t sure if she recognised him. But then there was a moment of recognition. Her eyes twinkled. She drawled out a “Heyyyyyy” as she smiled. And then she kept dancing.

  Throughout, her mouth hung open slightly. It felt like something between a smile and a scream. Her pupils were dilated, and her skin was flushed. Her breath came in rapid bursts, but she wasn’t panting like someone tired – she was panting like someone trying to keep pace with an invisible beat.

  Thomas forced himself forward, elbowing past a boy with a water jug and a woman muttering Hail Marys under her breath.

  “Let me through, please,” he said, to no one in particular.

  His hands were sweating. His stomach was tightening.

  It was her. It was Gretchen. Yet everything about it felt wrong. His eyes scanned over her body, analysing her movements. Every part of his mind grasped for reason.

  A fever? Hallucination? Poisoning? A seizure caught mid-loop?

  But her movements weren’t entirely chaotic. They had rhythm, albeit some terrible rhythm he couldn’t hear. However, he could see in the beat of her steps and the way her shadow flickered across the cobbles that there certainly was a rhythm to it.

  Thomas noticed that the old man also seemed to have some sort of rhythm. On the other hand, the plump woman and the younger boy did not appear to have any observable rhythm!

  Thomas instinctively relied on his training. “Observe. Describe. Don’t assume.”

  Her gait: unsteady but repetitive.

  Her balance: inconsistent; she nearly fell twice, but somehow her body always snapped her back upright.

  Her eyes: responsive, reactive.

  She saw him. She saw everything. She even invited him to join her, extending her arm out every now and then.

  And yet she kept dancing. She never stopped, not even for a brief pause!

  Thomas stood just inside the edge of the circle, unable to move for a moment. The other dancers continued moving, fast and frenzied. The plump woman had started to moan softly with each step. The old man cried out as a toenail split and blood smeared across the stones.

  The crowd’s murmuring was getting louder. A few clapped – likely a mock applause. Some crossed themselves. A boy tossed a coin into the circle. Thomas flinched at the sound of it hitting the ground.

  He stepped forward towards Gretchen, but she didn’t flinch.

  He whispered, barely audible over the thudding feet, “Gretchen.”

  But she was already turning again. She laughed once. It was a high, strange, breathless sound.

  “I love dancing, Thomas,” she suddenly said in a strained voice. Her eyes fixed on him with a conscious effort, but she continued dancing. Her lips had contorted into a troubled expression as she looked at him. “But this… this feels like penance!”

  Her words struck Thomas, but he didn’t have time to reflect. Her voice cracked on the last few words, not from emotion but exertion. Her knees buckled, her back spasmed once as if something deep inside her had seized. But she didn’t stop.

  Thomas moved hurriedly, his cloak already sliding off one shoulder as he reached for her urgently, all calm abandoned. He didn’t care who saw. Their dalliance had been a well-kept secret so far. That didn’t matter at this moment. He saw her suffering in front of his very eyes, and he had no name for the disease.

  He broke through the last ring of bystanders, shoulder brushing past a wool seller and a boy with a slop bucket. The world narrowed. Gretchen moved in front of him, caught in a faltering, violent rhythm. She spun half a turn, tripped, then lunged forward – not towards him or towards anything in particular. It looked like her limbs were answering a sound only she could hear. Her braid was undone. Dark strands clung to the side of her neck, slick with sweat. Her dress was soaked through, smeared with dark streaks where the crushed rye had begun to ferment against the fabric. A bit of spit was visible around the corner of her mouth, and her breath came in heaves. Her eyes were glassy and unfocused, mostly staring into the middle distance. They intermittently focused on Thomas, but not continuously.

  Thomas felt his stomach hollow, as if something cold had taken root there and bloomed in an instant. His training, his reason, all the neat rows of symptoms and causes he’d copied into his notebooks, lay scattered. He forced himself to speak. “Gretchen.” She didn’t stop. Her legs jerked, too fast for her upper body to keep pace. Her bare feet slapped against the street in that beat that seemed to have a rhythm, yet appeared irregular at the same time. Something primal – maybe a struggle between body and mind?

  Thomas stepped in front of her and grasped her arm. Her skin felt warm under his touch. “Gretchen,” he said again, louder now, a bit of a whisper-shout. His fingers found her shoulder. “Enough." She placed one hand on his shoulder and kept moving, but she now slowed down her pace. Her breathing hitched. Her head turned towards his. Her eyes darted from him to something beyond – towards the sky, the edges of the crowd, the chapel’s stone eaves – searching wildly. Then they steadied on his gaze. In that moment, her panic broke. Her expression softened and her knees buckled. Thomas caught her as she fell, wrapping his arms around her before she hit the ground. Her weight struck him with more force than he expected. She gasped once, like someone surfacing from water, and then collapsed against his chest. He held her tightly, wrapping his cloak around her now exposed shoulders, pulling it close to steady her. She didn’t flinch now, she barely moved, except for a small, insistent rhythm coursing through her – a slight tapping of her fingers against his collarbone. Her pulse throbbed erratically beneath his hand.

  “Are you alright?” Thomas asked tenderly.

  She smiled in response, and then closed her eyes wearily.