Chapter 1

The night Ronan Blackwood's hunting ships set White Reef ablaze, I took off my royal crown and boarded the Black Sail alone.

If he spared the merfolk still alive, he could keep me.

The human boy who'd been promising to marry me since we were children now commanded the most ruthless pirate fleet in Grayhaven.

In his cabin, he seized me by the waist and kissed me hard, leaving me breathless. He claimed me with such desperation that it was clear the years apart had only made him crave me more.

We spent three days in his cabin. At dawn on the fourth, I stirred as he slipped his arm out from beneath my head. I was still lying on my side when he emptied a basin of scale-eating brine over my back. I screamed and fell from the bed, curling up on the floor.

He stood over me with the empty basin, his knuckles white.

“Ready to tell me where you've hidden my parents?”

He blamed me for his parents' disappearance.

After that, he made me take out my tideheart to heal Vivian, who was carrying his child.

He made me dance for her in shackles, barefoot on a deck strewn with broken shells. Whenever I came close to dying, he'd gather me into his arms, call me by the name he'd used when we were children, and feed me the most expensive medicine a sea witch could brew.

“Lila, don't make me hate you.”

I no longer had the strength to ask which of us was forcing the other. He'd told me merfolk couldn't die. But a mermaid kept captive, cut off from the sea's free currents for three years, would dissolve into foam until nothing remained of her, not even her name.

I had three days left. Then, at last, I wouldn't have to love him anymore.

Chapter 1

The hatch slammed against the wall as I lay over a leaking plank, trying to lick seawater from the crack. A sailor hauled me up by my hair. “Lady Blackwood's sick again, and you're down here sleeping?”

He meant Vivian. They weren't married yet, but everyone aboard the Black Sail already knew what to call her.

I tried to tell him I hadn't been asleep. All that came out was a rasp. He slapped me, impatient with the effort of listening, then caught the chain around my ankle and dragged me out. The old wounds on my back scraped over the ladder until my vision went black. By the time he threw me into the captain's cabin, I'd left a broken trail of blood across the oak floor.

Ronan sat beside the bed, warming Vivian's hands between his own. His black night-watch shirt hung open, exposing the old scar beneath his collarbone. I'd stitched that wound myself, out on the reef. He'd been so worried about my cold hands that he'd enclosed them in his palms, needle, thread, and all.

“Reef venom,” he said. His gaze caught on my back for a moment before returning to my face. “Come here. Use your tideheart.”

Vivian reclined against the pillows and held out her bandaged wrist. Her silk nightgown stretched over the gentle swell of her belly. The moment she caught me looking, she shrank against him. “Don't let her look at our baby like that. She's scaring me.”

Before I could lower my eyes, his palm cracked across my face. “I warned you to stay away from her.”

I waited for the ringing in my ears to fade, my head still turned from the blow. “All right.”

His hand stopped in midair. Slowly, he closed it into a fist and lowered it.

I crawled to the bedside and unwound the bandage. Two tiny rows of teeth marked Vivian's wrist, the edges of the bites stained blue. Merfolk only developed venom in their saliva when they were starving. Vivian had been teasing the captives in the hold with food again.

“Is it bad?” she asked me, slipping her other hand inside Ronan's open collar to rest against his bare chest. “I don't want anything happening to our baby.”

He covered her hand with his and murmured that everything would be fine.

I undid the neck of my ragged dress. My fingertips brushed the wound on my chest, which still hadn't closed from the last time.

“Out,” Ronan told the sailor by the door. The man hesitated a second too long. Ronan drew his knife and drove it into the doorframe. “Did I stutter?”

Once the door shut, he tossed his sea coat over my waist and legs. That would've given me hope before. Now I just wanted to get this over with.

I pushed my nails into the flesh beneath my breastbone. When they touched my tideheart, the pain folded me to my knees. I drew out the silver-white pearl, fine strands of blood stretching between it and the open wound. It held my heartbeat and my soul. To Ronan, it was a supply of medicine that would never run dry.

He caught my shoulder to steady me, then let go when he saw the blood spilling down my chest. “Your blood was enough last time. Do you have to make a show of it? Is this supposed to make me feel guilty?”

I shook my head. I didn't explain that my blood had long since lost its power to heal. He'd taken enough of it to fill every rum glass on the ship.

The pearl's faint light fell over Vivian's wrist, drawing the blue from her skin. She opened her eyes, looked at me, and tilted her face up to kiss the corner of his mouth. “That's so much better. Hold me closer, darling. I'm still cold.”

He gathered her against him and stroked her cheek with his thumb. I remembered that hand against my own face, though even the ache came slowly now.

Vivian smiled at me over his shoulder, then covered her nose. “The smell of blood might bring the reef fever back. Could she leave us for a while?”

Ronan looked at me. His lips moved, but when he finally spoke, all he said was, “Go.”

I pressed the tideheart back into my chest. Too weak to stand, I braced my palms against the floor and crawled toward the door. Behind me, he quietly scolded Vivian for going near the hold. “Those things bite. Next time you want a look, I'll have someone keep them behind the net.”

I had barely crossed the threshold when a bucket of cold water hit me in the face. Meg, Vivian's maid, stood over me with the empty pail and a look of disgust. On the places where my scales had peeled away, it felt as though my wounds were being torn open again.

“What's with the act? It's not like you can die. Look at the mess you've made of the captain's floor.” She threw a piece of stiff, scratchy sailcloth at me. “Clean it up. Leave so much as a stain, and tomorrow you'll be dancing with your feet nailed to the deck.”

I knelt outside the cabin and worked my way along the bloodstains. Every time I cleaned a patch of floor, another drop fell from my chest. The door hadn't closed properly. Inside, Vivian complained that her ankles were cold and asked Ronan to take off her stockings himself. Her voice was soft and intimate, pitched so I'd hear every word.

I bent over the sailcloth and wrung it out. My tears soaked into it without turning to pearls. I was almost too worn out even to cry.

At daybreak, one of the last three silver scales on my wrist fell away.

Chapter 2

The first morning bell rang as I finally wiped away the last stain. When Ronan opened the cabin door, I was trying to hide the bloody sailcloth beneath my skirt. His boots stopped in front of me. “Where's all that blood coming from?”

I drew my shoulders in, afraid of staining his trousers. He crouched and grabbed my wrist, then immediately loosened his grip. “I asked you a question.”

“It's clean now.” I clutched the cloth. “I'll go.”

He watched me with something almost wounded in his eyes. Time after time, I'd let that look make me forget who'd taught me to be afraid of him.

Meg's voice carried across the deck. “She traded me a tear pearl for a needle yesterday. Said she wanted to mend the captain's old wristband. Anything to get back in his good books.”

Another woman laughed. “She picked up that little trick fast enough. His parents don't even have graves, thanks to her, and she's still trying to get into his bed?”

I closed my eyes. Ronan's fingers tightened around my wrist again.

He took me to the interrogation cabin beside the powder magazine. A black iron cage hung above a tank of electric eels caught in the Storm Sea. Fine copper mesh enclosed the bars. My legs shook at the sight of the crank.

“Tell me the route,” he said, locking the cage door. “If you won't tell me where they are, at least tell me when you last saw them.”

I opened my mouth, but the tide oath tightened around my voice, bringing blood into my throat.

I'd sworn it three years ago to keep his parents alive. Until the sealed tide ended, I couldn't reveal whether they lived or where they were to any human who still hunted merfolk. If I spoke, wrote it down, or even led a hunter to the refuge, its protection would break. The tracking curse buried in his parents' bodies would burn them to ash before anyone could reach them.

I'd tried explaining, even writing a letter. All I'd left on the paper was blood from my fingertips.

“Wait for the Blue Tide.” I gripped the bars and looked at him. “Ronan, please. Two more days.”

The last of the patience left his eyes. “Another two days? Lila, I've been waiting three years.”

He turned the crank. The copper net snapped tight, and the current tore through my wet wounds. My body jerked against the bars. I struck my forehead on the iron, unable even to scream as the barely healed flesh over my chest split open again.

He threw the crank back almost at once, wrenched the cage open, and caught me. His shaking hand couldn't hold the back of my neck. “Breathe. Lila, look at me. Take a breath.”

My mouth worked without sound, like a fish dumped onto dry land. He pressed his ear to my chest and stayed there until, finally, he let out a shuddering breath. His lips touched my temple. “I don't want to do this to you. Just tell me. Please.”

I raised a hand to his jaw and felt the stubble he hadn't shaved. “Then stop.”

He didn't answer. I let my hand fall and turned my face away.

Someone brought a sharkskin case to the door. I saw the White Reef crest engraved on its corner and went still. Those were the tidehearts I'd entrusted to a vendor in the harbor. The souls of my dead kin slept inside them. If I could get them home to our trench, they might still wake.

Ronan opened the case and took out a deep blue pearl.

“Don't touch it!” I lunged forward, the chain tearing through the flesh around my ankle. “Whatever you want, do it to me. Give it back!”

He watched the sudden strength in my hands, his face hardening. “So there is something you care about.”

He put the pearl beneath his boot. I heard it break and flung myself onto the floor, digging my nails into the seams between the boards. The blue light drained out of the scattered pieces.

“Whose was that?” He crouched and tipped my face up. “Your father's? Your mother's?”

My lips shook too badly for me to answer. His thumb swept a tear from my cheek. His own eyes were red, but he kept the rest of the pearls out of my reach. “I'd like to know if mine begged someone the way you're begging me.”

“Ronan, I wish I'd never met you on that beach.”

He kissed me so hard it felt as though he meant to force the words back down my throat. I didn't fight him. I didn't kiss him back, either. He only stopped when he tasted blood. “Don't say that.” He rested his forehead against mine. “You can't take that from me, too.”

I'd been six that summer, and he'd been nine. Merfolk children practiced taking human form in the shallows. The first time I grew legs, I managed fewer than ten steps before falling straight into his lap as he sat mending a fishing net.

He refused to let go of me. He asked Captain Evelyn if he could take me aboard and marry me when we grew up. Laughing, she lifted me out of his arms and told him he'd have to learn to ask what I wanted first.

After that, whenever the Black Sail came into port, he brought me a glass bottle. Sometimes it held candy from the harbor, sometimes a red ribbon or a cheap silver ring he'd found at a market. I kept every one.

The merfolk hunters began appearing when I was seventeen. My father forbade me to go near the coast, but I slipped away at low tide to see Ronan. He was waiting at the bow. He pulled me into his arms and introduced me to his crew as the girl he'd been waiting for.

He didn't call me a siren. He didn't call me a monster. As long as he was there to catch me, I'd believed there'd always be somewhere on land where I belonged.

When I was twenty-three, his parents represented Grayhaven's fleet at the signing of a treaty with White Reef's royal family to end the hunts. Their ship caught fire that night, and neither captain was seen again. A survivor said the last thing he'd witnessed was me pulling them into the sea.

That much was true. The rest of the truth had been locked inside me by the oath.

Ronan took up his parents' captain's seal, and his hunting ships began sailing into White Reef. I boarded his ship alone for the second time in my adult life, hoping I could make him stop. He cried when he kissed me. I thought that meant I could still bring him back to me.

The tide shackles he'd fastened around my ankle had never opened again.

“Lila?” He lifted me off the floor, then looked down at his sleeves. My blood had soaked through them and was dripping from his elbows.

I watched, almost wanting to laugh. “Don't bother wiping it off. In two days, I won't be making a mess anymore.”

His arms tightened sharply. “Get the ship's doctor!”

The neck of a bottle struck my teeth. He poured sea-witch medicine into my mouth so fast I choked, then wiped my face with his own sleeve as I coughed.

Vivian had appeared in the doorway. In a gentle voice, she suggested a salt bath. Merfolk healed faster in salt water, after all. Ronan unfastened the chain from its ring in the wall, leaving the shackle on my ankle, and lowered me into the copper tub the doctor had prepared. His hand stayed beneath my head.

The bleeding stopped almost immediately. Then a gray-white film began creeping over every scale the water touched. I smelled the bitter tang of powdered sea glass. It sealed wounds, but it also sealed the gill slits a mermaid needed to breathe.

“Change it.” I caught his wrist. “There's something wrong with the water.”

He bent to examine my wounds, as if he couldn't believe the medicine he'd given me wasn't enough to save me. “Don't be afraid. Let it close first.”

Behind him, Vivian put a finger to her lips. Looking straight at me, she silently mouthed, “I won't let you live long enough to see the Blue Tide.”

Chapter 3

Once, I woke to Ronan holding me. The bathwater had been changed. His shirt was soaked.

“I never meant to kill you. You know I can't bear to lose them.”

He took my hand and held it to his cheek. I eased it out of his grasp and pressed it over the wound in my chest.

When I next woke, he was gone. Sailors dragged me up to the quarterdeck, where the noon sun had baked the boards hot. My tideheart throbbed sluggishly. Every breath felt like swallowing a mouthful of salt.

Ronan sat beneath the awning with Vivian beside his knee, tying a new wristband around his arm. The old one I'd mended had been thrown down by the table leg.

“I saved you some lunch.” Vivian looked up with a welcoming smile. “You're so thin. It breaks my heart to see you like this.”

I couldn't answer quickly enough. Meg kicked me in the waist, sending me sprawling in front of them. Ronan caught her ankle and shoved it away. “Did I say you could touch her?”

The maid went white. Vivian immediately doubled over, clutching her stomach. “Don't get angry, Ronan. The doctor said I can't take a fright in my condition.”

He let Meg go. When he noticed fresh blood spreading through my skirt, he laid his coat over me, but his voice hardened again. “Get up. She's trying to be kind. You don't have to make this awkward for everyone.”

The moment he looked away, Vivian stepped on the coat's hem. I'd barely pushed myself upright when the cloth jerked tight and pulled me back to the deck. She widened her eyes as if surprised, then set a tin plate of meat and sea lettuce beside me. “Well, you can eat there. I don't suppose merfolk care much about table manners.”

Ronan looked at the plate on the floor. His fingers tightened on the arm of his chair, but he didn't ask anyone to give me a place at the table. I lowered my eyes to the food. I needed whatever strength I could get.

I reached for the food. Only then did Vivian lift her shoe from the coat and point to the pale meat. “Try that. It cost a fortune. Our little one will be eating it someday, too.”

I swallowed a small mouthful. My tongue was too numb to taste much. The meat caught in my dry throat. I tried to swallow again, but my stomach convulsed.

I doubled over and brought it all up. Vivian screamed and jumped back. Vomit had splashed her skirts and the pearl buckles on her shoes. She turned to Ronan, her eyes filling. “I was only trying to feed her! Why does she hate me so much?”

A sailor grabbed my hair. To keep me from hurting anyone with a mermaid's song, they forced a piece of cork packed with iron filings into my mouth and strapped it in place. Ronan lifted Vivian into a chair and knelt to clean her skirt himself.

He'd done that for me once. I'd been nineteen, attending my first winter ball in Grayhaven, when I spilled red wine down my dress. He'd dropped to his knees to wipe it away. Even his father had laughed and told him he was completely gone on me.

Now he knelt in front of another woman while I waited for his permission to spit the thing out of my mouth.

“Don't punish her,” Vivian pleaded, catching his hand between little sobs. “Let her keep me company while I paint my charts. That'll make us even, won't it?”

Ronan unbuckled the strap. The cork brought blood with it when he pulled it free. He asked someone to fetch clean water. “Why do you have to keep going after her?”

I pressed my lips together to stop the bleeding and waited for the water.

At the far end of the deck, the navigator rang the brass bell. The harbor officials had arrived and wanted Ronan to check the last passage permits before the Blue Tide. He stood, but Vivian caught his hand and drew him down to kiss her forehead. Then she placed his palm against her belly, watching me the whole time. “We'll be right here waiting for you.”

I turned my face away. Once, the thought of Ronan becoming a father had made me smile without even trying. I'd never imagined being chained at the feet of his child's mother.

As soon as he left, Vivian kicked over the plate. “You're blocking my light. Go sit by the rope basket.”

I moved slowly across the deck and rested my back against the sun-warmed rail. A torn red ribbon lay among the discarded ropes. I stared at it for a long time.

I left the ribbon among the ropes. Ronan still had the other tidehearts. I could never bring back the soul he'd crushed beneath his boot, but I had to find the others and get them home.

Two maids passed on the other side of the deck, praising Vivian's new chart and complaining about the trouble it took to make the colors.

“Three tidehearts for that little bit of blue. And we still haven't got enough white.”

I caught the rail and slowly pulled myself up. A faint sound reached me on the wind, the low keening White Reef merfolk made only when they were dying. I followed it. With every step, the shell fragments left in my feet from dancing sank deeper, but I couldn't stop for them now.

Behind the awning, several merfolk lay piled on a tarpaulin. Their tail fins were gone. Vivian was opening the last one's chest with a silver-handled filleting knife. She lifted out a pale gold tideheart, inspected it, and dropped it into a mortar.

The pestle came down. The keening stopped.

She looked up and smiled as though I'd come to save her the trouble of calling for help. “Lila, perfect timing. Royal tidehearts are silver-white, aren't they?” She came closer and laid her bloody hand on my shoulder. “Ronan would give his life for our baby. Of course he'd let your people make a few sacrifices. Why don't you pick one out for me? It'll be easier than trying them one by one.”

Chapter 4

She pulled back another tarpaulin. The boy in the glass tank lifted his head and pressed his small palms against the pane. “Lila!”

It was my ten-year-old brother, Noah. When I'd left White Reef three years ago, he still hadn't learned to fold his tail into legs. I'd promised that when the next Blue Tide came, I'd take him to see the candy shops by the harbor. Now hunting hooks pinned his tail to the bottom of a tank, and his blood had turned the water pink. “Take me home, Lila.”

I threw myself toward him, but someone stepped on my chain from behind. Vivian laughed. “Your brother? Well, that saves us looking any further.”

Two sailors lifted him out. He was too little to put up much of a fight. When they pinned him to the table, his tail kept searching for water. I dropped to my knees in front of Vivian and caught her knife hand. “Take mine. I won't fight you. You can have all the blood and scales you want. Please, just leave him alone.”

She looked down at me and stroked her belly. “But the baby doesn't like to be kept waiting.”

The blade touched Noah's chest. I pulled at her skirts with everything I had, hitting my forehead on the edge of the table. Blood blurred my sight. Noah wrenched a hand free, grabbed her wrist, and bit down hard. “Don't hurt my sister!”

Vivian's scream reached Ronan as he came onto the quarterdeck. He rushed over and kicked Noah away from the table. Noah fell into my arms, his mouth bleeding. A little tooth bounced across the boards and disappeared into a crack. I reached for it, but I couldn't catch it.

Ronan moved in front of Vivian, his face livid. “You taught him to bite her? You'll use a child now?”

I held Noah close, trying to wipe the blood from his mouth. “He's ten.” My voice shook so hard I could barely get the words out. “Look at him, Ronan. He's only ten.”

His eyes dropped to my brother. Then Vivian cried out in pain, and he looked away. “What did my parents ever do to you? They treated you like their own daughter, and you handed them over to the monsters in the sea!”

“Give me those last two days.” I caught his boot. “I'm not asking for anything else. Just let us live until then.”

Noah still had his fist in my skirt. He kept trying to burrow deeper into my arms, terrified I'd leave him, just as he'd done when he got lost in the trench as a little boy.

Ronan stared down at my hand. “You still have a chance. Tell me the route, and I'll let him go.”

The tide oath closed around my throat again. Blood flooded my mouth. Hearing me struggle for breath, Noah reached up to touch the place that hurt. He tried to wipe my chin clean and asked me if it was very bad.

I looked up at Ronan, wanting him to feel this desperation for the first time. “You'll find out. And when you do, don't ever say my name again.”

His face went white. He turned his back on us, his voice breaking across the words. “If she won't talk, her brother can pay for it.”

The sailor beside us drew his knife. I tried to crawl backward with Noah in my arms. “No! Ronan!”

By the time he turned, the knife was coming down. The small body against mine jerked. I heard something break inside his chest, and the light that should have shone for so many years beneath the sea went out in my hands. Noah's lips parted, but he never managed to say my name.

I looked up at Ronan.

“I hate you.”

His lips parted, but nothing came out. He dropped to his knees, reaching for my face with a hand that shook. I turned away before he could touch me.

“Lila, please.” His voice cracked. “Look at me.”

I adjusted Noah's head against my arm.

“Please.” Ronan leaned closer, trying to catch my eye. “Say something. Anything.”

When he reached for Noah, I pulled away, holding my brother against me.

His hand stopped. I covered Noah's chest with my skirt instead. He'd always hated the cold. Even before we went swimming, I used to have to coax him into the water.

Vivian suddenly crouched beside me and reached out as if to help. I didn't move, but she fell backward anyway, clutching her stomach. “I already told them to stop! Why would you push me, Lila? What has my baby ever done to you?”

Ronan caught her. He looked at me as though waiting for me to defend myself. With Noah in my arms, I remembered his first trip into the shallows. Ronan had told him what a beautiful tail he had.

“You saw what happened.” My voice was quiet.

He didn't answer. A little fluid seeped beneath Vivian's skirt. Meg screamed for the doctor, and Ronan lifted Vivian and carried her toward the captain's cabin. As he passed me, he paused. “Once the baby's born safely, we'll talk.”

I didn't lift my head. After everything, what could we possibly have left to talk about?

The sailors tore Noah out of my arms and dragged me back to the hold. I caught the doorframe and asked where they were taking my brother. A boot heel came down on the back of my hand. Then the hatch slammed shut.

Above me, they made up a bed for the birth. I heard basins being carried back and forth, Vivian crying out, Ronan promising her that no one would ever take their child away. With my swollen fingers, I searched the wet planks for the little tooth. It took me a long time to remember that it hadn't fallen down here.

By the following evening, I couldn't feel the floor anymore. The last silver scale came loose from my wrist and dissolved into foam before it reached the boards. I opened my hand. Light passed straight through it; I could see the dark bottom of the hold beneath my palm.

The Blue Tide had returned.

A baby began to cry upstairs, and Grayhaven's bells rang out to welcome a ship. The sound reached through the planks into what was left of my awareness. When we were little, that bell had always sent Ronan running to the docks to wait for his parents to come home.

Footsteps hurried overhead. Outside the ladder, someone shouted that the old captains were back. I tried to lift my head, but I couldn't hold it up. They'd made it home safely at last. The words I'd guarded for three years could finally be spoken, and all that escaped my throat was a breath too faint for anyone to hear.

More footsteps came. I couldn't tell how much time had passed. Several people had come. An iron key struck the lock twice before it slid into place.

“She's in here.” Ronan paused, his voice dropping, suddenly gentle. “Mom, Dad, don't worry. I only kept her from leaving—”

The door opened. I saw Evelyn first. She still wore the blue coat she'd had on the night the ship went down, one brass button missing from its collar. Gareth stood behind her with the key to my tide shackles clenched in his hand.

I wanted to smile at her and tell her I'd kept my promise. She dropped to her knees in the doorway instead. Ronan rushed past her.

He tried to gather me into his arms. This time, all they caught was a handful of foam, already coming apart.