BackBirch’s Vow: Blood and Thorn

Chapter 17 - Truth Serum

SOREN

The air in the training yard still hums with the aftermath of magic—ozone and iron, the scent of lightning trapped in stone. I step back through the doorway, the heavy oak thudding shut behind me, but I don’t walk away. Not yet. I press my ear to the wood, listening. Silence. No shouts. No crashes. No snarls.

Good.

That means they’re still alive.

And more than that—still touching.

I push off the wall, exhaling slow. My hand curls into a fist at my side, the crumpled photograph still inside it. Birch had given it back to me after Kaelen’s outburst, her fingers trembling, her face pale. She didn’t say a word. Just handed it over and turned away, like she couldn’t bear to look at it anymore. Like she couldn’t bear to look at *him*.

And I get it.

I’ve seen the way he looks at her. Like she’s the only air in the room. Like if she vanished, the world would stop turning. I’ve seen the way she fights—furious, brilliant, reckless—as if she’s trying to burn herself out before the fire consumes her. I’ve watched them tear each other apart, rebuild, tear again, like their love isn’t a bond but a battlefield.

And now this.

A fake photo. A lie dressed in truth. And it’s working.

Because Birch is starting to doubt. Not just the photo. Not just Lysara. But *him*. And that’s dangerous. Not just for them. For all of us.

Kaelen’s not just an Alpha. He’s a weapon. And Birch? She’s the only thing that keeps that weapon from turning inward.

I glance down at the photo again. The image is sharp—Kaelen’s back, Lysara’s body wrapped around him, the date stamp glaring like an accusation. But I know the truth. I was there when it was taken. Years ago. Before the ritual. Before the bond. Before *her*. It was part of the political marriage ceremony—Lysara demanded a “private moment” with the Alpha to seal the alliance. Kaelen refused to consummate it, but she still had the chamber documented. Always planning. Always manipulating.

And now she’s using it to break them.

I crush the photo tighter, the paper tearing between my fingers. Then I turn and stride down the corridor, my boots echoing on the stone. I know where I’m going. The Undercroft Archives. Deep beneath the estate, where old magic and older lies are stored in glass and steel.

And where the truth serum is kept.

The Archives are cold.

Not just in temperature—the air bites at my skin, even through my leather jacket—but in feeling. The walls are lined with shelves of black stone, crammed with scrolls, vials, and cursed relics. Glass cases glow faintly with trapped spells. The floor is polished obsidian, reflecting the dim light like a pool of oil. At the center of the room, behind a wrought-iron gate, sits the Truth Vault—a circular chamber lined with runes, its door sealed with blood magic.

I stop in front of it, my breath fogging in the air. Then I press my palm to the lock. My blood sings in response—Beta of Blackthorn, sworn to the Alpha. The runes flare red, then fade. The door swings open with a low groan.

Inside, the air is still. No torches. No light. Just a single pedestal, and on it—a vial of liquid so clear it’s almost invisible. Truth serum. Distilled from moonbloom, silverleaf, and the tears of a bound oath-keeper. One drop, and a person can’t lie. Not even in thought.

I reach for it.

And freeze.

“You’re not supposed to be here.”

The voice is soft. Female. Fae.

I turn.

Elara stands in the doorway, her silver hair spilling over her shoulders, her eyes like frozen stars. She’s dressed in court robes of pale blue, her fae glamour shimmering faintly around her. She shouldn’t be here. Fae aren’t allowed in the Undercroft Archives without permission.

And she knows it.

“You’re not supposed to be here either,” I say, not moving.

She steps inside, her bare feet silent on the stone. “I could say the same about you. But I know why you’re here. And I know why you need that.”

“Then you know I can’t let you stop me.”

“I’m not here to stop you,” she says. “I’m here to help.”

I narrow my eyes. “Help how?”

She reaches into her sleeve and pulls out a small crystal vial—identical to the one on the pedestal. “I have my own.”

My breath catches. “Where did you get that?”

“From the Fae High Court,” she says. “We keep one in reserve. For… diplomatic incidents.”

“And you’re giving it to me?”

“Not to you,” she says. “To *her*. To Birch. She needs to know the truth. Not just about the photo. About everything.”

My chest tightens. “You think she’ll take it?”

“No,” she says. “But she’ll believe *me*. And if I tell her the serum is real, that it can prove Kaelen’s innocence… she’ll listen.”

I study her. “Why do you care?”

She looks at me—really looks—and for the first time, I see it. Not just duty. Not just family. *Fear*.

“Because if they break,” she says, voice low, “the whole system collapses. The Blood Concordia Pact isn’t just about power. It’s about balance. And Birch? She’s the fulcrum. If she falls, the world burns.”

I exhale. Nod. “Then let’s make sure she doesn’t.”

I find Birch in the gardens.

Not the grand courtyard where the nobles gather, but the hidden one—overgrown, wild, tucked behind the east wing. She’s sitting on a stone bench, her back to me, her hands in her lap. The bite mark on her neck is visible now, the collar of her tunic loose, the skin around it still faintly red. She’s not crying. Not moving. Just… still. Like she’s waiting for the world to decide her fate.

And that terrifies me.

Because Birch doesn’t wait.

She *acts*.

“You’re not supposed to be here,” I say, stepping forward.

She doesn’t turn. “Neither are you.”

“Fair.” I sit beside her, leaving space between us. The bond hums—faint, but present. She feels it too. We both do.

“I brought something,” I say, holding up the vial.

She glances at it. “Truth serum.”

“You know about it.”

“My mother used it,” she says. “Before the ritual. To prove she hadn’t broken the coven’s oath.”

My chest tightens. “And did she?”

She looks at me. “She didn’t have to. She died before they could test her.”

I nod. “Then you know how it works.”

“One drop. No lies. No omissions. Even thoughts are exposed.”

“And you know what it can prove.”

She turns away. “I don’t need proof. I need *certainty*.”

“They’re the same thing.”

“No,” she says. “Certainty is knowing. Proof is believing.”

I exhale. “Then let me help you believe.”

She doesn’t answer.

Just stares at the garden—thorned roses, black ivy, wolfsbane growing wild. This place was once Kaelen’s mother’s sanctuary. Now it’s forgotten. Like so many things here.

“You think he’s lying,” I say.

“I don’t know what to think.”

“You know *him*,” I say. “You’ve seen him lose control. You’ve seen him fight for you. You’ve seen him hold a blade to his own throat to prove he’d rather die than lose you. And now you think he’d go to her the same night he marked you?”

She flinches. “It’s not just the photo. It’s the *timing*. The way he wouldn’t tell me what happened. The way he looked at me when I asked.”

“He looked guilty,” I say. “Because he *was* with you. All night. He fed the bond. He held you. He didn’t leave. But he couldn’t tell you, because he didn’t want you to see the photo. Didn’t want you to have to look at her touching him. Didn’t want you to think—” My voice drops. “—that he ever wanted her.”

Her breath hitches.

“And he didn’t,” I say. “Not like that. Not ever. The bond was political. Cold. She used it to control him. To humiliate him. To break him. And now she’s using it to break *you*.”

Tears burn her eyes. “Why didn’t he tell me?”

“Because he was afraid,” I say. “Afraid you’d run. Afraid you’d use it against him. Afraid that if he let himself *hope*—” I echo his words, “—he’d lose control. And he can’t lose control. Not with you. Not when everything’s at stake.”

She presses her fingers to the bite mark. “And this?”

“A claim,” I say. “Not a trap. A vow. He marked you because he couldn’t *not* mark you. Because the bond was screaming. Because you said, *‘I choose it.’* And he finally believed you.”

Her breath hitches.

“But the photo—”

“Is fake,” I say. “Spliced. Old footage. She’s been using it for years. Kaelen didn’t want you to see it. Didn’t want you to have to carry that weight.”

She looks at me. “And you believe him?”

“I’ve served him for over a century,” I say. “I’ve seen him lie. I’ve seen him manipulate. I’ve seen him kill without blinking. But I’ve never seen him look at anyone the way he looks at you. Like you’re the only thing keeping him alive.”

Tears spill down her cheeks.

“Then why do I doubt him?” she whispers.

“Because you’re afraid,” I say. “Afraid of needing him. Afraid of wanting him. Afraid of *loving* him. And Lysara knows that. She’s not just attacking him. She’s attacking *you*. Your trust. Your certainty. Your *choice*.”

She closes her eyes. “I don’t want to fight him anymore.”

“Then don’t,” I say. “Fight *for* him. With him. Not because of the bond. Not because of duty. But because you *want* to.”

She opens her eyes. “And if I do?”

“Then you’ll win,” I say. “Because he’ll fight for you too. And when two people like you love each other that fiercely—” I hold up the vial. “—no lie can survive.”

She stares at it. Then at me.

And slowly, she takes it.

We find Kaelen in the armory.

Of course we do.

He’s sharpening his dagger, the whetstone moving in slow, deliberate strokes, the blade catching the torchlight. His back is to us, his muscles taut, his jaw clenched. He doesn’t turn. Doesn’t speak. Just keeps working.

But he knows we’re here.

“You wanted proof,” I say, stepping forward. “Here it is.”

He glances at the vial in Birch’s hand. His jaw tightens. “You don’t need that.”

“Yes, I do,” she says, voice steady. “Because I need to know. Not just believe. *Know*.”

He sets down the dagger. Turns. “And if I refuse?”

“Then I walk away,” she says. “And you never see me again.”

My chest tightens.

He stares at her. Gold eyes burning. “You’d do that?”

“I have to,” she says. “Because if I stay, if I fight for you, I need to know it’s real. That you’re not just trapped. That you don’t wish it was *her*.”

He exhales. “You know I don’t.”

“Then prove it,” she says. “Not with words. Not with kisses. With *action*.”

He looks at the vial. Then at her. Then nods.

“One drop,” he says. “And you’ll know everything.”

She steps forward. Uncorks the vial. Holds it out.

He doesn’t hesitate.

He tilts his head. Opens his mouth.

She lets a single drop fall.

It hits his tongue. He swallows.

And then—

He stills.

His eyes close. His breath hitches. When he opens them, they’re not gold.

They’re human.

And full of pain.

“Ask,” he says, voice rough. “Anything.”

She steps closer. “Did you go to Lysara last night?”

“No.”

“Did you leave my chambers after you marked me?”

“No. I stayed. I held you. I fed the bond with my blood. I didn’t leave.”

“Did you ever want her?”

“No. Not as a mate. Not as a lover. The bond was political. Forced. I never touched her. Never kissed her. Never wanted her. I only ever wanted one woman. And she’s standing in front of me.”

Tears burn her eyes.

“And the bite on her neck?”

“A political display. A lie she’s used to manipulate me. I never claimed her. I never loved her. I only ever loved one woman. And she’s standing in front of me.”

“And the photo?”

“Fake. Spliced from old footage. She’s been using it for years. I didn’t want you to see it. Didn’t want you to have to carry that weight. Didn’t want you to think I ever wanted her.”

She presses her fingers to the bite mark. “And this?”

“A vow,” he says. “Not a trap. I marked you because I couldn’t *not* mark you. Because the bond was screaming. Because you said, *‘I choose it.’* And I finally believed you.”

Her breath hitches.

“And if I’d died in the Trial?”

“I would’ve died with you,” he says. “The bond wouldn’t have let me survive. But I’d rather die than see you belong to Virellion. Than see you belong to anyone else.”

She steps forward. Presses her forehead to his.

“Then make me believe,” she whispers. “Not with words. Not with threats. With *action*.”

He doesn’t answer.

Just pulls her into his arms, his body pressing into hers, his heat searing through the thin fabric of her clothes. His breath hitches. His heart thunders against her chest.

And then—

He turns her.

Not rough. Not forceful. Gently. Carefully. Until she’s facing him, her legs straddling his, her hands braced on his shoulders. His eyes search hers—human, burning, *alive*.

“You’re so fucking beautiful,” he whispers. “Even like this. Even broken. Even hating me.”

“I don’t hate you,” she breathes.

“Then why do you fight it?”

“Because I’m afraid.”

“Of what?”

“Of needing you. Of wanting you. Of *loving* you.”

He stills.

Then—

He kisses her.

Not soft. Not slow.

Hard. Desperate. A claiming. A promise.

And I know—

This isn’t just survival.

This isn’t just desire.

This is the beginning.

Of everything.

I turn. Walk away.

Because some things aren’t meant to be witnessed.

And some vows?

They’re meant to be kept in silence.