Prologue

Teresa prayed silently to the Virgin as she hauled herself to her feet, clinging grimly to the bedpost until the room stopped spinning. She could imagine her old nurse María’s horrified cries even now: Doña Teresa, it’s too soon to rise from your childbed! Yes, it was…but Teresa couldn’t afford to wait. Come morning, the servants would be sending word to her husband in Sevilla. When he heard the news…

Hail Mary, full of grace, the Lord is with thee. Blessed art thou among women, and blessed is the fruit of thy womb — Beneath the ritualized words, other prayers. That she wouldn’t stumble in her dizziness and fall. That the night air would not be too cold. That the tiny handful of servants her husband had allowed to accompany her out here, to her family’s old estate, were all abed and would not hear her moving about.

That her sole remaining hope would not be in vain.

Teresa prayed as she gathered up her newborn daughter and wrapped the tiny infant as warmly as she could. The Blessed Virgin had laid her son to rest in a manger, for lack of anywhere else to put him — but the Holy Land was surely warmer than Andalucía in November. Protect my little girl, please, Teresa thought, clutching her daughter to her chest. And…forgive the blasphemy of what I go to do.

The Virgin watched over Teresa, or else simple luck was on her side. She slipped out of the house without anyone the wiser, and outside the night was cloudless. It made the wind bite sharper, but the moon sailed resplendent in the sky above, silvering the ground with a guiding light.

A childhood of wandering this countryside steadied her feet as she struck out past vineyards whose gnarled grape vines rose from the soil to grasp at trellises like damned souls, past groves of orange trees whose boughs sagged under the weight of fruit still too green to harvest. Too young, too young. Blessed María, I only want my child to live. If that’s a sin, then every mother is a sinner. Planting kisses on the babe’s soft brow, praying it was not the only baptism her daughter would receive, Teresa left the cultivated fields behind and stumbled across the rocky ground beyond, into a copse of trees.

The branches overhead painted the ground with shadow, and she took as much care as she dared, picking her way past roots and autumn leaf fall. Head bowed to watch her step, she somehow still missed the burred casing of a fallen chestnut. Her ankle rolled, pain stabbing up into the core of her even as more warmth rushed down her thighs. Wrapping her arms around her daughter in a protective curl, Teresa braced for the hard ground.

Thin arms caught her, wiry with strength and rough as bark against her cheek. For a moment she was transported back to her girlhood, dark hair crowned with a tangle of twigs, leaves, and chestnuts armored in spikes, skirts hiked and knees scraped from climbing as high as she could into the boughs of her favorite tree. And all around her — taunting from above, urging her on from below, at her side, supporting her when she slipped…

“Castaña,” she gasped. A silly name, a childhood name, given to a creature who could not share her own. “Please, I need…”

“Little Tere. Back again so soon — weren’t you just here?” With care that belied the roughness of her bark skin, Teresa’s savior settled her gently among the roots of a massive chestnut. Castaña once claimed that tree was old before the birth of Christ, and Teresa believed it. Her friend spoke often of the past: not just the Moors who once ruled this place as al-Andalus, but those who came before them, Visigoths, Romans, Greeks, Carthaginians, the tribes of the Turdetani.

Peoples Castaña had known first-hand.

“It has been a year, my friend,” Teresa said, uncovering her daughter’s head enough for Castaña to see what she carried. “And I have another daughter for you to meet.”

“This isn’t the same one as before? It looks the same.” Castaña peered dubiously at the child. “Are all you humans this purple and wrinkled when you come out? It’s like a little chestnut!”

Grin splitting her sharp, narrow features, she poked a spindle-thin finger at the crown of the baby’s head. Teresa batted it aside before it could touch the soft spot. “Castaña, I need your help. My daughter needs your help.”

It came spilling out of her in a jumbled mess, past and future mixed together: six previous daughters born to Teresa, her husband’s growing rage at the lack of a son. His threat, when he learned she was bearing again. “He — he said that if I whelped another girl, he would drown her like an unwanted puppy –” She didn’t dare let go of her daughter, but she spared one hand to clutch at Castaña’s arm. “Please, you must protect her!”

The teachings of the Church were very clear: faeries had no souls. They lacked an understanding of good and evil, and so they could never be trusted. To have any dealings with them was heresy, and those who sinned in such fashion might be burnt at the stake.

But against that, Teresa laid two clear facts: first, that she would burn if it meant her daughter could live. And second, that Castaña was her friend.

Her hopes crumbled like old ashes when Castaña said, “I can’t.”

Teresa had no strength to resist when the faerie took her little daughter out of her arms, tilting the infant’s face into the moonlight. “I’m just a dryfoot faerie, rooted here in the mortal world. Even if my magic could protect her, its strength would not last. The moment she touched iron, or one of your holy relics, or a dozen other wards your kind have against mine, it would burn away like morning fog.”

Gently, she placed Teresa’s daughter back in her arms and crouched at her side, limbs bent and twisted like the branches of the great tree above. “And even if they preserved her for a short while, what of you? That husband of yours will keep plowing you for sons until you’re as dry and dead as overworked ground.”

Teresa flinched, not at Castaña’s prediction, but at the vicious way she spat the word husband. “What else can I do? I must bear him a son.” If she even could. Old María said it was a faerie blessing on one of her ancestors, that they would be fruitful — but not in equal measure. Like all faerie gifts, it was double-edged. The mortal world did not value daughters.

Castaña’s head tilted to an unnatural angle. “What if you had a son?”

Her loins ached in reply. Frustration and desperation forced tears from Teresa’s eyes, despite her efforts at control. “I have prayed and prayed, to no result! All I can do is hope –”

“Or let me help you.”

“What do you mean? Can you — could you –” The thought was too impossible to voice. Surely even a faerie could not effect such a change. If any such herb or charm existed in the Otherworld…

The Inquisition would suppress all knowledge of it. They would not want good Christians thinking they could alter the form God had decreed their bodies should take.

When Castaña spoke, though, her words were not the absurd hope flowering in Teresa’s heart. “I could take your daughter’s place.”

“But — you’re a woman,” Teresa said. Which was far from the only barrier, but it was the one her tongue shaped first.

All around them, the trees rustled, not in any breeze. Other faces appeared among the branches, wilder, shyer. Castaña was not the only faerie in this grove, but Teresa had only rarely glimpsed the rest; they knew all too well what the Church did to their kind. For them to show themselves now…

One twig-fingered hand waved away such distinctions. “Woman. Man. Aren’t these simply games you humans play? What difference is there between the two, save for a bit of extra flesh no one’s allowed to see? When first we met, you told me you’d be in trouble if you befriended a boy, so for you I was a girl. Now you need a son. I could be your son.”

The price, the price, isn’t there always a price? Worry beat in time with Teresa’s heart. She clutched her daughter closer as though Castaña would spirit her off while Teresa was too weak to stop her. “You mean to steal my daughter away.”

She knew the stories: infants snatched from their cradles, changelings left in their place, little cuckoos claiming a human nest. There were ways to get one’s child back, but…

“Not steal. Trade. Your daughter will be raised by my folk.” Castaña gestured at the trees around her, the half-seen faces watching with wide eyes. “And I, by you. Your husband gets a son — albeit not quite the one he imagined — and you are safe.”

Unless someone discovered the truth. But even that would be better than what Teresa had now: a peril farther down the road, with more time to plan and prepare.

Yet the watching fae made her wary. “Why would you offer this? We have been friends since my childhood, yes, but…to enter my world is no small thing.”

The night wind had picked up, and it felt like a portent, like a shift of the world on its axis. Moonlight danced through the leaves, its glimmer submerged in the ageless depths of Castaña’s eyes. “And I would do so with no small purpose. In fact, I would require a promise from you, on your name and your lineage. That you will help me learn how your people are conquering the Sea Beyond.”

Exhausted, cold, wrung out from giving birth, Teresa could not at first encompass Castaña’s meaning. The Sea Beyond, the faerie Otherworld that lay beyond the Pillars of Hercules — conquest, for the profit and power of His Most Catholic Majesty — what did that have to do with her daughter?

Nothing. But everything to do with Castaña.

It was an impossible request, one Teresa had no idea how to fulfill. She was the wife of an insignificant hidalgo, living far from the court in Madrid, from the port of València through which that commerce and conquest flowed. She knew nothing of such matters.

But fulfillment of that promise was a peril farther down the road. Here, now, her priority had to be the safety of her daughter.

Teresa looked down at the tiny, vulnerable infant in her arms. The priceless treasure her husband threatened to destroy, simply because it wasn’t the boy he wanted, the heir society demanded. “My little girl…she will be cared for among your people?”

“Of course,” Castaña said, as the trees rustled in agreement. “Babies are rare among us. We treasure those we have.”

Surely a life in the grove would not be so terrible. Teresa had always been happiest when she could escape to run wild among the trees. And if her husband was pleased with his son, he might allow her to visit the estate. To know her seventh daughter, if only a little. Perhaps even — “Will you let me have her baptized?”

Castaña’s head shook like the limbs of the trees above. “That is the one thing you must not do. She cannot be consecrated to your Lord, or all my protections will vanish. I’ll be exposed as a changeling, and you will burn in your Inquisition’s fires. For my safety and yours, you must not seek her out. Leave her with my people. Forget she exists.”

The words caught in Teresa’s throat like thorns. Forget her daughter? Impossible. As soon forget her own heart.

But the rest…

Castaña was right. She could not be a secret mother to this child. She must keep her and risk her husband’s wrath — or let the infant go, and trust the faeries to love her as she deserved.

“I promise,” Teresa whispered.

Her arms didn’t want to unbend. She forced herself to place a final kiss on her daughter’s brow, biting back a whispered name that baptism would never have the chance to bestow. Then, with almost physical pain, she held her daughter out to Castaña. “Be safe, little one. Safer than my love alone could ever make you. And may God watch over you, wherever you go.”

***

“Doña Teresa! What are you doing here?”

Teresa dragged herself out of the dark and into wakefulness. She ached all over, her body cold and stiff from sleeping on the floor of the little chapel. Old María helped her upright, joints creaking even more than Teresa’s own. “You should be in bed, my lady, and –”

A soft noise stopped the old servant’s chiding. María almost dropped Teresa. “Is that your daughter on the altar?! She can’t be here; she’ll take a chill!”

Then shocked silence, as María abandoned her mistress to scoop up the child.

Teresa staggered to her feet on her own. The swaddling cloths had been pulled aside, the infant nestled among them like a chestnut in its casing. Showing, very clearly, the male child within.

“I prayed,” Teresa said unsteadily, as María stared at her. “To the Blessed Virgin. She must have heard my prayers.”

It was a thin lie to cover the truth. But surely María would not think a faerie could be here, in a holy place. Or that Teresa might trade away her seventh daughter in order to get a son.

The weight of that trade would haunt Teresa for the rest of her life.

María’s hands moved as if of their own accord, bundling the child up again. “It was dark in the birthing room,” she said, her uncertain tone at odds with the brisk efficiency of her hands. “And I am old. A foolish error — my fault. I’ll make sure the other servants know.”

Servants loyal to this house and this family. Teresa’s family — not her husband’s.

“Thank you,” Teresa whispered.

“No need to thank me,” María said, sounding more like herself. “Now, let’s get you and this babe to bed.”