“A failed one. For goodness’ sake, put that away.” Both of them knew that if Hazel were found guilty of theft from a sailor, she’d wear a placard and shackles in the hold until her feet touched land.

“No one but you will ever know,” Hazel said, slipping the knife back into her pocket. “Unless I need to use it.”

One afternoon a sailor lost his footing and fell from the yardarm to the deck, a distance of about twenty feet, near where Hazel and Evangeline sat together prying apart wet rope. They looked up. No one was coming to his aid. Hazel dropped the rope and went to his side, leaning close and whispering in his ear. The sailor howled and groaned, clutching his leg.

Just then the surgeon emerged from the tween deck. Seeing Hazel bent over the sailor, he called, “Move aside, prisoner.”

At first Hazel ignored him, running a hand down the crewman’s leg to his shin, probing it with her fingers. A small crowd had gathered. Looking up at the surgeon, she said, “His leg is broken and needs to be reset.”

Evangeline was struck by the girl’s expression: an air of practiced attentiveness that gave her an unexpected authority.

“I’ll determine that,” the surgeon said.

The sailor groaned.

“He’ll require a splint. And some rum,” Hazel said.

“What experience have you?”

“My mother is an herbalist. A midwife.”

The surgeon flicked his hand at her. “Stand over there.” Crouching over the sailor, he repeated Hazel’s movements: he felt down the man’s leg, grasped it between his fingers, put a flat hand to his forehead. Sitting back on his heels, he said, “Someone find a board to transport him to my quarters.”

“As I said,” Hazel murmured behind him.

Several days later, Evangeline awoke to find Hazel on the floor between their berths, hunched over sprigs of dried herbs, crushing leaves with two fingers.

“What are you doing?”

“Mixing herbs for a poultice. That sailor could die if infection sets in.”

Hazel had been right: his leg was badly broken. A convict who brought his meals to the infirmary reported that he was delirious with pain, thrashing and cursing. They’d had to tie him to the bed.

“The surgeon knows what to do, doesn’t he?” Evangeline said.

Hazel gazed at her with those implacable gray eyes. Then she gathered the herbs into a heap on a rag and tied them into a parcel.

Early in the afternoon, Evangeline sat on the main deck with a small group of convicts, mending a sail. She watched Dr. Dunne come up from the tween deck, a grim expression on his face, and vanish around a corner. Putting down her needle and thimble, she told the woman beside her she was going to the privy. She caught up with him at a spot blocked from view by a stack of crates. He stood at the railing, resting his chin on crossed arms.

“How is the sailor?”

He looked up. “Not well.”

She, too, crossed her arms on the rail. “Hazel, the girl—”

“I know who she is.”

“I saw her crushing herbs. For a poultice, she said.”

“She’s not a doctor.”

“Of course not. But if there’s nothing to lose . . .”

“Only a man’s life,” he said in a clipped voice.

“He’s doing poorly, I hear. What harm is there in trying?”

Shaking his head slightly, Dr. Dunne gazed out at the shimmering line between sky and sea.

Back in the sewing circle, Evangeline watched as he called Hazel over, leaning toward her as she pulled a small packet from her apron pocket and opened it for him to inspect. He crumbled the herbs with his fingers, held them to his nose, tasted them with his tongue. Then he took the packet and disappeared down the ladder.

Perhaps the result was circumstantial. Perhaps the sailor would have recovered regardless. But three days later he sat lounging on the main deck in a wooden chair, his splinted leg propped on a barrel, pestering a blond-ringleted convict and bellowing with laughter at her retort.

Medea, 1840

The surgeon had his hands full. All the beds in the infirmary were occupied. Heatstroke, seasickness, diarrhea. Delirium, ulcerated tongues, dislocated limbs. He treated constipation with calomel, made of one part chloride and six parts mercury. For dysentery he prescribed flour porridge with a few drops of laudanum and a tincture of opium. To reduce fever he shaved women’s heads, a treatment they feared more than delirium. For pneumonia and tuberculosis, bloodletting.

Word of Hazel’s miracle cure had spread. Convicts who didn’t want to see the surgeon or who were sent away untreated began lining up to see her. She scrounged herbs from the cook and planted some of the seeds she’d smuggled on board with her in a box of manure: arnica for pains and bruises, mandrake for sleeplessness, and pennyroyal, a flowering mint, for unwanted pregnancy. For dysentery, egg whites and boiled milk. For fainting spells, a tablespoon of vinegar. She created a paste from lard, honey, oats, and eggs as a salve for chapped hands and feet.

“That girl, Hazel, with her witchy powders and potions . . . ,” the surgeon said irritably to Evangeline as she stood at the railing late one afternoon. “I’m afraid she’ll only make things worse.”

“You have plenty to do. Why should you mind?”

“It gives the women false hope.”

She gazed out at the water. It was clear and green, as smooth as a mirror. “Surely hope isn’t a bad thing.”

“It is if they forgo proper medical treatment.”

“The sailor who fell from the yardarm is much improved. I saw him shimmying up a mast.”

“Correlation, causation. Who’s to know?” His mouth tightened. “There’s something about that girl. An insolence. I find it . . . off-putting.”

“Have pity,” Evangeline said. “Imagine being her age, condemned to this.”

Giving her a sidelong look, he said, “The same could be said about you.”

“She’s much younger than I am.”

“How old are you, then?”

“Twenty-one. For another month, at least.” She hesitated, not sure whether it was appropriate to ask. “And you?”

“Twenty-six. Don’t tell anyone.”

He smiled, and she smiled back.

“Hazel’s life has always been hard. She’s never seen . . .” She struggled to find the words. “The . . . good in the world.”

“And you have?”

“Of a sort.”

“It seems to me you’ve had a rather rough go of it.”

“Well, yes. But the truth is . . .” She took a breath. “The truth is, I was rash and impulsive. I have no one to blame for my misfortune but myself.”

The wind was picking up. Sunlight splintered brightly in shards across the waves. For a few moments they stood silently at the railing.

“I have a question,” she said. “Why on earth would anyone choose to be on this ship if they don’t have to?”

“I’ve wondered that many times myself,” he said with a laugh. “The easy answer, I suppose, is that I’m restless by nature. I thought it would be an interesting challenge. But if I’m honest . . .”

He’d been a shy only child, he told her, raised in Warwick, a small village in the Midlands. His father was a doctor; it was expected that his son would join the practice and take over when he retired. He’d been sent to boarding school, which he loathed, and then to Oxford and the Royal College of Surgeons in London, where he discovered to his surprise that he actually did have a passion for medicine. On returning to the village he purchased a charming cottage with a housekeeper and set about expanding and updating the practice. As an eligible bachelor, he became a frequent guest at banquets, balls, and shooting parties.

Then disaster struck. A young lady from a prominent landholding family was brought in complaining of stomach pains and shaking with chills, and had a high fever. His father, having never seen a case of appendicitis, diagnosed typhoid, prescribed morphine for the pain and fasting for the fever, and sent her home. The heiress died in great agony, vomiting blood in the middle of the night, to the disbelieving horror of her family. Their heartbreak required a villain. The doctor and his partner-son were shunned, the practice ruined.

Some months later, an envelope arrived in the post from his roommate at the Royal College. The British government sought qualified surgeons for transport ships and would pay handsomely. It was a particular challenge to find surgeons for the female convict ships because, “to be frank,” his roommate wrote, “the ships are rumored to be floating brothels.”

“A gross exaggeration, as I now know,” Dr. Dunne hastened to add. “Or at least . . . an exaggeration.”

“But you signed on anyway.”

“There was nothing left for me at home. I would’ve had to start somewhere new.”

“Do you regret it?”

The corners of his mouth turned up in bitter comedy. “Every day.”

This was his third voyage, he said. He spent little time with the rough sailors, the boorish captain, or the alcoholic first mate, whose excesses he’d already treated several times. There was no one he could really talk to.

“What would you do, then, if you could do whatever you chose?” she asked.