“Don’t interrupt, Holmes!” Lowell cried.

Agassiz assented to Holmes’s question with a heavy silence.

“But the Cochliomyia macellaria can only digest dead tissue,” Holmes protested. “There are no maggots capable of parasitism.”

“Remember the eight thousand undiscovered flies I’ve just spoken of, Holmes!” Agassiz rebuked him. “This was not the Cochliomyia macellaria. This was a different species altogether, my friends. One we had never seen before—or didn’t want to believe existed. A female fly of this species had laid eggs in the patient’s nostrils, where the eggs hatched and the larvae developed into maggots, eating right into his head. Two more of the men on Devil’s Island died of the same infestation. The doctor saved the others only by cutting out the maggots from the noses. Macellaria maggots can only live on dead tissue—they like corpses best. But the larvae of this species of fly, Holmes, survives only on living tissue.”

Agassiz waited for reactions to show on their faces. Then he went on.

“The female fly mates only once but can lay a massive number of eggs every three days, ten or eleven times in their monthlong life cycle. A single female fly can lay up to four hundred eggs in one sitting. They find warm wounds on animals or humans to nest in. The eggs hatch into maggots and crawl into the wound, tearing through the body. The more infested is the flesh with maggots, the more other adult flies are attracted. The maggots feed on the living tissue until they drop out and, some days later, become flies. My friend Coquerel named this species Cochliomyia hominivorax.”

“Homini… vorax,” Lowell repeated. He translated hoarsely, looking at Holmes: “Man-eater.”

“Exactly,” said Agassiz with the reluctant enthusiasm of a scientist with a terrible discovery to announce. “Coquerel reported this to the scientific journals, though few believed his evidence.”

“But you did?” Holmes asked.

“Most certainly,” Agassiz said sternly. “Since Coquerel sent me these drawings, I have studied medical histories and records of the last thirty years for mentions of similar experiences by people who did not know these details Isidore Sainte-Hilaire recorded a case of a larva found inside the skin of an infant. Dr. Livingston, according to Cobbold, found several diptera larvae in the shoulder of an injured Negro. In Brazil, I have discovered on my travels that these flies are called the Warega, known as pest of both man and animals. And in the Mexican war, it was recorded that what people called ‘meat flies’ would leave their eggs in the wounds of soldiers left on the field overnight. Sometimes the maggots would cause no harm, feeding only on dead tissue. These were common blowflies, common macellaria maggots such as you are familiar with, Dr. Holmes. But other times the body would be ravished with swellings and there would be no saving what was left of the soldiers’ lives. They’d be hollowed out from the inside. You see? These were the hominivomx. These flies must prey on the helpless, people and animals: That is the only means of their offspring surviving. Their life requires ingestion of the living. Research is only now beginning, my friends, and it is very exciting. Why, I collected my first specimens of the hominivorax on my tour of Brazil. Superficially, the two types of blowflies are very much the same. You must look at the deep coloring; you must measure with the most sensitive instruments. That is how I was able to recognize your samples yesterday.”

Agassiz dragged over another stool. “Now, Lowell, let us see your poor leg again, will you?”

Lowell tried to speak, but his lips were shaking too violently.

“Oh, don’t you worry now, Lowell!” Agassiz broke into a laugh. “So, Lowell, you felt the leetle insect on your leg, then you brushed it away?”

“And I killed it!” Lowell reminded him.

Agassiz retrieved a scalpel from a drawer. “Good. Dr. Holmes, I want you to slip that into the center of the wound, and then pull it out.”

“Are you sure, Agassiz?” Lowell asked nervously.

Holmes swallowed and knelt down. He positioned the scalpel at Lowell’s ankle, then looked up into his friend’s face. Lowell was staring, his jaw open. “You won’t even feel this, Jamey,” Holmes promised quietly, comfort just between them. Agassiz, though only inches away, kindly pretended not to hear.

Lowell nodded and gripped the sides of his stool. Holmes did as Agassiz said, inserting the point of the scalpel into the center of the swelling on Lowell’s ankle. When he removed the scalpel, there was a hard white maggot, four millimeters at most, wriggling on the tip: alive.

“There, that’s it! The beautiful hominivoraxl” Agassiz laughed triumphantly. He checked Lowell’s wound for more and then wrapped the ankle. He took the maggot lovingly on his hand. “You see, Lowell, the poor leetle blowfly you saw had only a few seconds before you killed it so it had time to lay only one egg. Your wound is not deep and shall heal fully, and you shall be perfectly fine. But notice how the lesion in your leg grew with one maggot crawling inside of you, how much you felt it as it tore through some tissue. Imagine hundreds. Now imagine hundreds of thousands—expanding inside of you every few minutes.”

Lowell smiled wide enough to send his mustache tusks to opposite ends of his face. “You hear that, Holmes? I’ll be fine!” He laughed and embraced Agassiz and then Holmes. Then he began to take in what it all meant—for Artemus Healey, for the Dante Club.

Agassiz grew serious, too, as he toweled off his hands. “There’s one other thing, dear fellows. The strangest thing, really. These leetle creatures—they don’t belong here, don’t belong in New England nor anywhere in our vicinity. They are native to this hemisphere, that seems certain. But only in hot, swampier climates. I have just seen swarms of them in Brazil, but never would we see them in Boston. Never have they been recorded, by their correct name or any other. How they got here, I cannot speculate. Perhaps accidentally on a shipment of cattle or…” Agassiz lapsed into detached humor about the situation. “No matter. It is our good fortune that these critters cannot live in a northern climate such as ours, not in this weather and surroundings. They are not good neighbors, these Waregas. Luckily, the ones that did come here have surely died out from the cold already.”

In the way that fear readily transfers itself, Lowell had entirely forgotten the certainty of his own doom, and his ordeal was now a source of pleasure that he had survived. But he could only think of one thing as he walked silently away from the museum alongside Holmes.

Holmes spoke first. “I was blind to listen to Barnicoat’s conclusions in the newspapers. Healey did not die from a blow to his head! The insects were not just a Dantesque tableau vivant, some decorative show, so that Dante’s punishment could be recognized by us. They were released in order to cause pain,” Holmes said in rapid fire. “The insects were not ornament, they were his weapon!”

“Our Lucifer wants his victims not merely to die but to suffer, as the shades do in Inferno. A state between life and death which contains both and is neither.” Lowell turned to Holmes and took his arm.

“To witness your own suffering. Wendell, I felt that creature eating away inside of me. Ingesting me. Even though it might have only snacked on a small amount of tissue, I felt it as though it was running straight through my blood into my very soul. The chambermaid was telling the truth.”

“By God, she was,” Holmes said, horrified. “Which means Healey…” Neither man could speak of the suffering they now knew Healey to have endured. The chief justice had been meant to leave for his country house on a Saturday morning and his body was not found until Tuesday. He had been alive for four days under the care of tens of thousands of hominivorax devouring his insides… his brains… inch after inch, hour after hour.