No matter how many times Dr. Carlos Finlay traveled into the island’s interior, he never grew accustomed to the mosquitoes. Even in the pit of winter, the vermin found their way to the dry highlands, infesting sunny rocks and shadowy embankments, and haunting his sleep. This morning, however, it was not the mosquitoes that encumbered his journey, but an extraordinarily hot morning sun. Even with his trusty straw hat clamped firmly down all the way to his brow, he felt feverish, as if he were standing too near an oven door.​

            If mosquitoes and sun were bothersome, the thought of fever was downright chilling. Finlay knew fever too well. As a gawky boy he had survived bouts of cholera and typhoid, with their days and nights of infernal sweats and torturous deliria. He had survived them, but not completely. As a result of his two death-defying acts of dehydration, he was prone to heavy thirst and a sense of malaise in hot sun. A trip inland was not so bad if he remembered his water jug. This morning, as fate would have it, he had left his water jug in the stable at Santa Teresa and did not learn of this oversight until he stopped for a drink and the jug was nowhere to be found, either in his saddlebag or his cart. He’d unpacked everything onto the side of the road searching for it, all the while cursing himself vociferously for toting so much useless equipment. All the while the poor horse stood in the sun waiting patiently for its silly human to stop clattering around or babble himself out.

​            Finlay ultimately did both. But he did not do the smart thing, which would have been to ride back to Santa Teresa for his jug. No. After piling all his hygrometric, drosometric, and aërometric equipment back onto the cart, he rode on, convinced that Constancia was just over the next rise. Several hours later, his throat dry as flannel and his skin on the verge of erupting in flames off his body, Dr. Finlay suspected he had misjudged the distance.

            Within a few minutes, the road came to a low stone wall that Finlay remembered as the Constancia boundary marker. Shortly after, he arrived at the gate. At the end of the tree-lined alleyway stood the fat Grecian columns of the house and their delicious-looking shade.

​            The gate was closed but was quickly opened, to Finlay’s surprise, by Andreu Mateu i Balaguer himself.

​            “Well,” said Finlay gustily, overcome with relief that he had at last arrived. “It’s not every day the administrador himself comes to greet me!”

​            Andreu was taciturn. “What do you want, Finlay?”

​            Finlay reached down to grip Andreu's hand. Andreu shook it stiffly. “Perhaps a room?”

​            Andreu squinted up at him for a few moments and seemed unable to register Finlay’s face. He glanced at the cart and sighed.

​            “You’ll need to dismount.”

​            Finlay complied eagerly. There was shade by the gate, so he removed his hat and fanned himself. “Rather a hot morning, do you agree?” He quickly scanned the sky. “No rain coming, I think. Have you a drop of water for my parched throat?”​

​            “What were you doing at Santa Teresa?” the young administrador asked.

            Finlay’s thirst was like a beast in his chest. He retained his smile and continued to fan himself and said, “Would you believe I was staying the night there?”​

​            Andreu glared at Finlay's truculence. Finlay had forgotten that the planter’s son took his job very seriously. Like administradores everywhere, Finlay supposed. Andreu approached Finlay’s horse and studied the overfilled saddlebags. He lifted one of the flaps and peered in. “What is all this?”

​            “Sensitive equipment.”

            “What for?”

            “My work.”

            “What work?”

            “Meteorology, as always,” Finlay replied proudly. “It’s a hobby of mine, as you recall, but it’s not without academic merit.”

            Finlay stood watching while Andreu unbuckled each saddlebag and rifled through the contents. Hygrometers, drosometers, aërometers, Finlay got ready to say, but Andreu did not ask. The planter's son seemed more interested in the coils of wire and rope.

​            Finlay turned to the planter’s son and spoke in his friendliest voice: “Really, Don Andreu, what’ s going on? Are you in the midst of an uprising?”

            Andreu's eyes leveled on Finlay’s and held them uneasily. Then Andreu  patted Finlay’s arm and said, "Precaution.”

​            Finlay’s thirst roared like a typhoon. “That's fine. May I enter?”

​            “You know my father won’t stand for any of your talk about fever.”

​            Finlay was surprised. He was sure that if he didn’t get to water soon, he was sure he would either catch fire or shrivel up. “I have no interest in fever. You saw my equipment. I wish only wish to set up my equipment, take a few days' worth of atmospheric readings, and be off.”

​            “How many days?”

            “Two or three would be adequate.”

            “There are American guests.”

​            “That’s fine with me.”

​            Andreu's hands rose to his hips. “Last time you embarrassed my father.”

            “I did?”

            “You talked about fever quite a bit. You wanted to know if there had been any deaths involving—“

​            “The Black Vomit, yes,” Finlay cut in. At that moment, he regretted everything about his inquisitive nature and wondered whether because of it he would perish from thirst less than a hundred yards from water’s saving grace. He went on, a bit breathlessly: “I recall it plainly, yes, I spoke of it. But, you see, Don Andreu, it’s not fever season right now, at least not up here. So there is no need to talk of it, not at all.”​

​            "Very well," Andreu conceded. “You are welcome to the downstairs room.”

​            “Splendid!”

            Feeling a burst of energy, Finlay lifted the reins and waited for José to draw back the gate. Then he led the horse and the cart through the gate and up the shady lane.​​​

​

Finlay positioned the hygrometer on the branch of the ceiba tree and tapped its glass dial to relax the spring. He stood back and read the dial, and jotted the numeral in a column in his diary. Then he clapped the diary shut, tucked the pen behind his ear, lifted his sack of equipment, and moved on to the next location, a shady spot along the river.

            The day was warm and Finlay felt exuberant. His gadgets had survived the bumpy ride from Santa Teresa. His stomach was full of watered-down guarapo, poured for him by one of the pretty cooks. The air had a deliciously sticky feel to it that promised rain and interesting hygrometer readings later that evening. Finlay would check each of his seven hygrometers three times daily at a set time—morning, noon, evening—for the duration of his stay at Constancia, and notate his findings. It was an odd undertaking, he had to admit, but he was on to something, possibly something big.

            Atmospheric measurements were also the perfect pretense for getting away from the city. Business had been good since he’d opened up his medical practice right there along Havana’s fashionable Prado the previous year, and a half-dozen successful cataract surgeries had started him off on the right foot with Havana’s polished élite. Still, he missed the breezy plantation life of his youth, chasing lizards and crunching the strands of juicy cane between his teeth on a hot day. And the sting of coffee berries, slung at his backside like minuscule darts by his older brother Eduardo. Finlay did not fault his father for selling the plantation and bundling Finlay, Eduardo, and their mother off to France, but the quiet, slow pace of that old plantation had never left him.

            Finlay arrived at the river. There he suspended a hygrometer from a branch. He tapped its dial and recorded the reading, then climbed to the road and headed back to the house. He passed the barracón just as the noon bell rang. There was a shift in the rhythm that he noticed with all his senses: shirtless negros coming up from the fields handed off their machetes to the team that was headed down. Acrid cook-smoke thickened on the air. The trains sat still on the tracks, but only briefly. The pillar of smoke churning from the chimney of the casa de fuego cleared for less than a minute (Finlay counted the seconds) before turning slate-gray again. During the changeover, the mayoral’s men strutted through the crowd like peacocks, their lashes and irons prominently displayed. No doubt they imagined that everything was under their control.

            Finlay turned at the barracón and continued up the hill toward the infirmary. It was proper to present himself before Claude Desmarais, the plantation doctor, before the day grew too old.

​

The clinic was a madhouse. Negros writhed on all eight cots, moaning and swimming in their sweat. The floor was slick with effluvium and the air hot and fetid as a lower level of hell. Finlay caught sight of Desmarais administering medicine to a young man unable sit up on his own and who had to be held by the shoulders by two negro nurses (illegally, Finlay noted). The man’s face was contorted as if he were caught in the grip of a devilish nightmare. Despite the madness of the scene, Finlay managed to catch Desmarais' attention. When he saw Finlay, the French doctor's eyes darkened and he looked away.

            Taking the hint, Finlay went back outside. He and Desmarais did not know each other well, but Desmarais disliked him for all the usual reasons: youth, training, background. As a slave doctor, Desmarais' medical tool was brute force and his objective was to keep negro hordes slaving away. He did so without the benefit of fancy equipment or wealthy clientèle. Finlay, on the other hand, had been raised in Europe, trained in the United States, and ran a practice on the most prestigious street in Havana. The two men lived and moved in separate worlds.

            “Busy day for the doctor,” Finlay said cheerfully to an overseer who was standing nearby, his weapons dangling menacingly. The overseer ignored him.     

            Don Josep's men were renowned for their stolid demeanor, but Finlay liked to mess with them a little when he could.

            The overseer appeared to be guarding an older negro who was sitting on the ground, hand wrapped in a bloody cloth. “What happened here?’ Finlay asked.

            Again the overseer ignored him.

            “Say,” Finlay persisted. “I was just wondering. This illness that seems to be inflicting a few of the negros—" Here he cocked his head nonchalantly toward the infirmary door, through which faint moans of agony were still emerging. “—Is it not, by chance... fever?”  

            The overseer's stare hardened.

            “Never mind,” Finlay conceded with a chuckle. “Do forget I asked. Say, when you see the good French doctor, would you let him know Finlay is here? That’s Finlay. Dr. Carlos Finlay. Of Havana. He knows who I am. Will you do that for me?”

            The overseer scowled and said, “Get lost, Finlay.”

            Finlay sighed. Three words were a start. “Very well,” he said. He glanced down at the negro seated motionless on the ground, scarred forearms resting across drawn-up knees. The young African gazed off into the trees with an abandoned expression, as if he were observing a world beyond what anyone else could see.

            This one, Finlay thought, will be the first to fight.

​

            “Doctor Finlay,” said the patriarch, from his traditional spot at the head of the long table.

            “Yes, sir?”
            “What brings you to Constancia this time?”
            “Climatic research, sir,” Finlay replied confidently, taking in the glances of the American guests seated around him: two couples—one young, one old—and a plain spinsterlike lady. “Humidity, temperature, and atmospheric pressure," he explained. "I’ve placed a few of my instruments around the premises, but they’re quite out of the way.”
            “Good,” said the host with a cough of satisfaction. “I suggest you stay out of the way as well.”
            The remark brought polite laughter. Though smiling, Finlay felt himself reddening.
            “I do have a question, sir, if I may?” Finlay asked.
            Don Josep took an almost imperceptible breath. “Go ahead.”
            “The well, sir. At your old coffee settlement. Did you know that a few of the negros are using it?”
            “I was unaware,” said Don Josep. He looked at the Frenchman. “Claude?”
            “Perhaps I can clarify, sir,” said Desmarais. “You will recall that the well at the barracón was soiled last week. I suspect it may have to do with that.”
            “Makes perfect sense,” Finlay said good-naturedly. He dusted some bread crumbs from his sleeve and smiled around at the other guests. The young woman smiled back at him, winsomely, and he felt himself blushing again.
            “Claude, if the barracón well has been soiled, then it must be cleaned,” Don Josep said with a distinct edge of impatience. “The negros must not be obligated to walk to the old well for their water.”
            “It could be the cause of the illness," the young American woman chimed in. "Among the negros."

            Desmarais' eyebrows shot up. "Oh? How so, Mrs. Fletcher?"

            "Surely you've read Dr. Snow's research?" the young lady asked.

            The French doctor indulged a mean chuckle and looked around the table as if soliciting the amusement of the other guests.

            "The young lady is correct," Finlay interjected, giving the young lady a kind nod. To Desmarais, he said, "Even if you do not adhere to Dr. Snow's theory, it is worth investigating."

 

They stood in the soft shade beside the abandoned farmhouse and watched a woman draw water from the well. She poured water from the pail to a clay pot. As far as Don Josep could tell, the water was clear. Hefting the pot onto her hip, the woman hurried on down the hill without noticing any of the three men.

            There were no other negros fetching water, but the well had obviously been busy earlier, as the ground around it was muddy and well trodden.
            Don Josep remembered the day the well had been dug when he was a boy. It had taken half a dozen of his father’s negros a whole day to dig into the soft earth until it turned to mud in their hands. By sunset they had lined the pit with clay bricks and rigged the pulley and pail. Don Josep's father was offered the first drink from the tin cup, but he offered it in turn to his favorite negro, a mandingo called Celestino with keen eyes and a trusting heart.
            Amo, Celestino had said as scores of curious negros looked on, I have never tasted finer water than this.
            In response to Celestino’s appraisal, the entire slave population of Constancia—less than a hundred at the time—had erupted in thunderous applause, and Don Josep's father had never been more loved than he was that day.
            Much has changed since then, Don Felipe reflected.
            Don Josep started back down to the big house. Desmarais followed. They walked their horses into the barracón and went straight to the well. Dozens of negros gathered around silently. Men removed hats. Children jostled to the front. It was not every day that the patriarch rode into their midst.

            Still on his horse, Desmarais peered into the well. “The water is clear,” he remarked in English, so his words would not be understood by the gathering of negros.
            Don Josep dismounted and strode forward. He leaned over the edge. At the bottom, his reflection divided and rejoined. Desmarais' face appeared beside his. Desmarais sniffed the air, so Don Josep did likewise. The air rising from the well was cool and damp, but not putrid.
            Another reflection appeared alongside theirs. Both men looked up to see Finlay.
            “Smells clean,” Finlay remarked, smiling at the other two men in turn.
            Desmarais showed no response to Finlay’s appearance out of nowhere, but Don Josep was glad the Scots doctor had turned up when he did. Finlay was an educated man, for sure: schooled in Europe and the United States. Even if he was only an eye doctor, he had a youthful enthusiasm Don Josep welcomed. He did not care that Finlay had gotten on the bad side of the Havana royalists; if anything, Don Josep admired him for it.   
            To Desmarais, Don Josep said, “We must be sure.”
            As the other two men watched, Don Josep lowered the pail, dipped it, and drew it back up. The pulley creaked rustily. He lifted the tin cup from the edge of the well, dipped it in the pail, and brought it to his lips.

            Finlay’s hand shot out, stopping the cup. “Wait,” he said.
            “What is it?”
            “Don’t drink it.”
            “Why not?”
            Finlay breathed tensely. “Water that looks and smells clean may be infested.”
            “Infested,” Desmarais murmured under his breath. Shaking his head, he looked away.
            “With organisms,” said Finlay.
            Don Josep poured the cup out on the sill of the well. “I see nothing.”
            Finlay turned to Desmarais, suddenly. "It would explain the illness among the negros," he said.
            “The bloody flux,” Desmarais replied, “is under control.”
            “Dysentery?” asked Finlay.
            “Yes.”
            Finlay’s eyes narrowed. “The young American woman is correct about the work of Dr. Snow. He is an English physician. A few years ago, he traced the spread of a cholera outbreak to the handle of a water pump. If dysentery is spread by minute organisms in the same way, then everyone who drinks from this well will be infected.”    
            "Corruption is not caused by minute organisms," Desmarais objected. 
            “Are you calling my negros corrupt?” Don Josep asked. “Go ahead, Finlay.”
            Finlay thought for a moment, then said, “Ascaris lumbricoides.”
            “There are no roundworms in this water,” Desmarais grumbled.
            “I didn’t say there were!” Finlay’s voice was raised. He paused to collect himself before cotinuing. “You know that there are organisms smaller than roundworms, so small that they can be seen only under a microscope.”
            “And what makes you think they infest in well water?” Desmarais asked, eyes flaring.
            Finlay didn’t answer.
            Emboldened by Finlay’s silence, Desmarais turned to Don Josep. “Go ahead, sir. I assure you this water is safe to drink.”

            Don Josep glanced at Finlay, then back at Desmarais. He passed Desmarais the cup. “You first.”
            Desmarais stared at the cup.
            “You hesitate?” Don Josep asked.
            Desmarais dipped the cup and drank, then slung what was left on the ground. “The water is fine,” he growled. “Now, if you don’t mind, sir, I must be getting back to my work.”    
            “Go ahead!” Don Josep snapped.
            It was clearly not the response Desmarais had expected. The French doctor's eyes widened in surprise, then narrowed on Finlay, and for a moment Don Josep felt the low heat of envy simmering between the two men.
            Doctors.
            Without retort, Desmarais mounted his horse and rode away. The crowd opened to let him pass. Don Josep was relieved to have him gone. He looked back at Finlay and wondered if Finlay might not do a better job looking after the Constancia negros than that pompous Frenchman. Finlay was younger and more energetic and, in a word, brighter. Don Josep admired brightness. There wasn’t much of it at Constancia anymore, not even among the American visitors. Still, he would not accept laxity or indecision.
            “Is this water clean or not?” he asked Finlay quietly. "And please answer with a smile, as hundreds are watching."
            Finlay spoke quickly. “If there is dysentery among your negros, sir, it could be caused by living organisms that are too small to see. Like parasitic worms, only much smaller. These organisms could be the source of the contagion.”
            “I have heard of this,” said Don Josep.
            “It’s a theory,” Finlay said. “But a good one. All disease may be caused by tiny organisms. Unfortunately I can’t prove it. No one can. I can only speculate that this well is, in fact, contaminated with organisms that were passed along in human feces.”
            Don Josep yanked his hands from the sill and took a step back, horrified.

            “What?” he cawed.
            “Smell the air, sir. I caught the scent earlier today and went to verify it for myself: the negros are using human waste in their vegetable garden just up the hill. It is a common practice among slave populations, but a risky one. The contagious organisms are in the waste, you see. The rainwater has drawn the organisms into the groundwater and from there it has seeped into this well.”
            Don Josep pointed his nose toward the conucos and sniffed the air. Finlay was right. There was a foulness on the air.  
            “Extraordinary,” said Don Josep, feeling queasy. “How can you be certain?”
            “I can’t be certain, but I believe it’s true.”
            Don Josep took another step back from the sill. “Is the old well contaminated also?”

            “I suspect it is not.”

            Don Josep smiled at the young doctor warmly. "What next, then?" he asked.

            "Block this well, sir. Insist that the negros use only the other well. And provide them with proper fertilizer for their fields."

            Don Josep nodded. "And the ones who are sick?"

            "Give them plenty of water from the fresh well, sir," said Finlay. "And pray that their illness will pass."

            Don Josep nodded again. He turned and walked toward the crowd, the circle of negros facing him. Not a soul moved as they awaited his word.

            "My children," he said, in Spanish now. He smiled at them all. "Listen to me closely..."