The airport was packed. Families preparing for Christmas holidays, business-men rushing around to finish their work whilst snapping down the phone at one another. But despite all that, I finally felt a little more relaxed. The only thing better than an airport, as far as I was concerned, was actually being in the air. I'd always attributed it to being a daughter of Zeus, but then how would you explain Thalia and her irrational fear of heights?

My lips twitched at the thought as I shifted in line in front of the customer service desk, behind Nick and Olympia. The woman at the desk beamed widely in that fake-customer-service sort of way, with her blonde curls and bright blue eyes. "Good evening, how can I help you?"

"We need three tickets for a flight to Vegas," Nick told her calmly, already routing in his pocket for his wallet.

The woman clicked a few keys on her keyboard, then grimaced at us apologetically. "I'm afraid we have no seats left on our next flight."

Nick's shoulders sagged, but I slipped between him and his sister with a slight frown. "When is the flight?" I asked her.

She stared at me for a second. "It leaves in an hour, but-"

"There should be tickets left. Can you check again please?"

"Listen, sweetie-"

I flinched at the term, but continued all the same. "Please? They'll be under the name Grace."

For another second, she just looked at me, then at Nick, who was trying not to frown, and Olympia, who was smiling cheerfully. "Alright then," she sighed, re-clicking her keyboard again. Staring at the screen, she blinked in surprise. "Err, sorry about this, there… there must have been some mistake on the system, we do have reserved seats under the name Acacia Grace?"

"Really?" Nick scoffed, but I elbowed him harshly in the ribs.

"That's me. Can we check in please?"

The woman didn't look altogether convinced, and in the end, I had to show her the student ID card I had from the boarding school in New York to prove it was me. Finally satisfied, she quickly checked us in and handed us our boarding passes, before hurriedly shooing us away and serving the next customer.

"How did you do that?" Nick blinked when we were far enough away from the desk.

I shot him a withering look. "I'm the daughter of Zeus. I'm literally never stopped from getting on a plane."

"Oh look!" Olympia beamed, pointing at the tickets in my hand. "First class!"

We continued through the airport (I had to hold my breath the entire way through airport security because I was convinced that the numerous weapons we had would set off the alarms, though according to Olympia, celestial bronze 'wasn't that kind of metal') and decided to use the extra time we had spare to find some clean clothes and equipment.

"I still can't believe you haven't packed more stuff," Olympia mumbled at me with a touch of disgust as she eyed the tiny backpack over my shoulder.

I sighed. "We're fighting monsters, not walking down a catwalk. Food and weapons come first."

"Whatever you say," she muttered, disappearing into an expensive looking store to my left.

"Stay with Oly," Nick instructed, nudging me in her direction. "I'm just going to get some cash out for the casino."
An image of the Lotus Hotel and Casino from a couple of years ago flashed through my mind, and I shook myself. "Oh no, we're going nowhere near a casino. Not that again."

"You've never been in a bar, but you've been in a casino?" he frowned. "Aren't you a little young for that?"

I felt my jaw lock. "It wasn't a normal casino."

"Of course not," he laughed easily. "Look, if Oly says one of the guys is in Vegas, then they're probably up to their neck in trouble and it's probably in a casino. I'm just being prepared."

I didn't believe that for a second, but he only spun around and disappeared into the crowds to find an ATM. "Can't believe I'm doing this," I grumbled, stuffing my hands into my pockets and twisting to find Olympia.

As I turned, though, I caught sight of a familiar figure in the corner of my eye. On instinct more than anything else, I froze, staring awkwardly. It was the girl from The Concert Hall, the one I'd knocked into in front of Luke. I recognised the pale, slim face and the jet black hair and dark eyes. She was taller than me, older too, wearing torn black skinny jeans and a black sleeveless blouse that fell longer at the back than it did at the front. A golden chain sat around her neck, and similar chains clinked around the leather boots she walked in.

What was she doing here? And more importantly, why was she staring at me? Somehow, I doubted she was still annoyed about that drink.

"There you are!" Olympia's voice came, and I started in surprise. She frowned. "Are you alright?"

"Fine," I lied a little too quickly. "Look, I already have some things to change into. I'm just going to clean up and change, I'll meet you at the plane, okay?"

Her frown deepened. "I'm not sure it's a good idea to separate, Acacia."

If I'd been thinking straight, that would have been my first warning sign. As it was, all I could think about was getting a minute to myself, away from prophetesses and archers. So instead of accepting her warning, I smiled half-heartedly and took a few cautious steps back. "I'll be okay, I've been doing this long enough, right?"

Olympia scowled, but did nothing to stop me as I turned and strode away from her, shouldering my way through the mass of rushing crowds until I got to the other side of the hall. Breathing deeply, I pushed my way into the women's bathroom, groaning internally when I realised it was barely any quieter in here.

Ignoring the three giggling teenagers huddled by the furthest sink, I slipped into one of the cubicles and locked the door behind me. Focusing for a moment on one task, I moved methodically as I pulled the fresh clothes out of my backpack, set them on top of the closed toilet seat, and began to get undressed.

The moment I reached to pull my top over my head, a sharp stab of pain rushed into my skull and I gasped, snatching the shirt out of the way and lifting a shaky hand to my scar. In an instant, I was covered in blood.

"Damn it," I grumbled to myself, grabbing a fistful of tissue to try and clean it up. The very sight of so much made me sick to the stomach, but I gulped back as much cold air as I could and perched myself on the edge of the toilet, pressing the tissue into my skin as hard as I could stand.

I wondered for a second what Olympia and Nick would think if they could see the state I was in. Would they still help me? I scoffed to myself. A more accurate question would be, would they still let me help? The thought made my eyes roll. There wasn't anything anyone could do to stop it, so why should I let it stop me?

Besides, now I needed to finish the tests. Which reminded me, I had to think of a way to get a message to my father, if he didn't already know.

Outside the cubicle, the giggling girls wandered past and out of the bathroom, finally leaving me alone. I breathed a sigh of relief, flushing the bloody tissues away and carefully slipping a blue checked shirt over my shoulders.

Unlocking the door, I let myself out and cleaned the blood off my hands at the sink, grimacing at the sight of the scar in the mirror. It didn't look good – in fact, it looked a lot worse than the last time I'd seen it. The poisonous ink seemed to be gradually inching closer to my heart, down across the front of my chest. Pulling a face, I wiped the last bit of blood away and fastened up another couple of buttons.

I'd just turned toward the door when it swung open with a creak, and the same girl from The Concert Hall stepped in with an arrogant stride. She looked like about Olympia's age, with none of her kindness or optimism. Instead, her eyes were cold and cruel, with a wicked smirk and a dangerous glint in her eyes.

"So," she started, pushing the door shut and hold it there with a single hand. "I guess I should apologise, we didn't get a chance to talk properly in the bar, did we?"

I'd gone rigid on the spot, my fingertips twitching at my side, ready to grab the hunting knife in the back of my belt.

The girl grinned as though she knew what I was thinking. "No need for that, Grace, where are your manners?"

"Who are you?" I demanded.

Her eyes flashed and it was hard to tell which was the stronger emotion; amusement or anger. "Didn't Oly and Nick bother to tell you?"

"Tell me what?" Somehow, I managed to keep my face straight, but an uneasy feeling was stirring in the pit of my stomach.

"Dear me, Acacia, don't you ever learn? Everyone has their own agenda, especially the ones who can see what's coming next." Her face contorted in a mixture of anger and disgust. "She never trusted me, not really." My stomach jerked as I realised she was talking about Olympia. If the group prophetess didn't trust this girl, I figured she had a fairly solid reason.

"Either explain who you are, or get out of my way," I instructed, determined to sound much more confident than I felt.

The girl smirked, and made the slightest bowing gesture she could. "Are you always this rude to family? I'm Demetria King. Your cousin. First cousin, I might add. You don't have many of those after all, do you?"

First cousin… "That's not possible," I scowled, a growing fear clenching in my chest. "That means…"

Demetria flashed a wicked smile. "I'm the Daughter of Hades."

In the same second, my hand snatched around the hilt of my hunting knife. Her eyes flashed, but she made no move to stop me as I drew it out of its sheath. "Now, now, no need for all that. Far too messy and, well, there's a lot of potential for collateral damage." She jerked her hand toward the door, and I thought of all the families and children here to travel for Christmas.

Slowly, I lowered the knife back down.

"Good girl," she chuckled. "Luke said you'd be this predictable. Still, he was a fool for thinking you wouldn't get involved back at that bar. You and your dear friend Perseus Jackson have a habit of being in the wrong place at the wrong time."

"If you go anywhere near Percy-"

"Oh calm down, would you?" she dismissed with a hint of disgust. "Save your strength, you're going to need it. Don't want to waste it all on one single Son of Poseidon, do you?"

My jaw locked in irritation. "What do you want?"

"Social call," she shrugged. "I just wanted to meet my latest replacement."

"Replacement?"

She sighed. "They really haven't told you anything at all, have they? See, these other demigods you're going to fetch already know each other. They've been together since some of them were very young. Gods, Oly, Nick and I were only six when we found each other. The two of them were being chased by monsters, and wouldn't you know, a daughter of Hades is stronger than two children of Apollo. So I saved their miserable lives, like a young, naïve child would, not realising they didn't deserve any of it. Over the years, we found Ebony and Klaus and Myles and soon, it felt like I had a family. Friends."

I felt myself shift awkwardly on the spot, and she let out a short, dark scoff. "Then they stabbed me in the back. All because Oly saw something in the future. Someone." She fixed me with her cold, furious eyes. "You. Their protector. The precious Daughter of Zeus."

She spat my father's name like it was poison, and thunder rumbled in the distance.

If Demetria noticed, she didn't let on. She only strode forward, her face demented in fury. "I'll see all of you – all six of you – dead," she snarled under her breath, an inch from my face. Behind my back, my fingers twitched around the knife's hilt. "But first, I want to see the look in their eyes when they see you fall. When they realise you've failed them."

My heart pounded in my ears, blood rushing to the scar on my throat. Her eyes dropped to it, and she managed another evil smirk. "Good luck, Acacia Grace. I look forward to our next meeting."

With a last, warning look, she twisted and strode out of the bathroom, letting the door slam shut behind her.

A second later, I let out a breath I hadn't realised I'd been holding, shoving the knife back into its sheath and lifting my quivering hands to my face. Was she telling the truth, about her and the others? She knew all of their names, at least, and seemed to have a very personal grudge against all of them.

I glanced at my reflection through my fingers and gulped at the pale colour of my skin. I needed to find out the truth. Then I had to focus on getting the other three, and beating Demetria before I got too weak.

"Hades is still managing to make my life a living hell," I commented dryly to myself, washing the fresh blood from my scar and cleaning my hands.

Outside, Olympia and Nick were hovering by the doors of the store I'd left Olympia in. The moment they saw me, Nick scowled. "I thought I told you to stay with Oly."

"I ignored you," I replied easily. "They'll be boarding the plane soon, we need to get moving."

"Something's wrong," Olympia said carefully. "I can't see…"

My lips twisted. "Come on."

Cautiously, they followed behind me as I strode through the airport to the boarding gate. Again, the documents were checked (I had to use the Mist when they asked to see our passports) before we were herded onto the plane and shown to our seats. Nick chose the solitary seat in the aisle, scowling until I took my seat nearest the window, penned in by Olympia.

"Are you sure you're alright?" she asked me quietly.

I just grimaced and nodded, leaning back in my seat and waiting for take-off. My fingertips drummed, and my eyes fixed to the window, moving only to see the people boarding as they were herded aboard one by one. I could see Olympia and Nick trading awkward looks out of the corner of my eyes, but I tried to ignore them as best as I could.

Eventually, the plane began to creep down the runway, and I felt the tight feeling in my chest loosen slightly as I watched it disappear beneath the wheels of the plane.

"I met someone at the bar earlier," I said carefully. "And again at the airport."

Olympia was quiet for a second. "Oh? I'm guessing there's a point to this?"

"It was Demetria King."

Silence again. I risked a glance over my shoulder to see her staring at me, her expression tight and her eyes glassy. "She's gone back west…" She blinked and shook herself once. "What did she tell you?"

"That she met you when you were six, that she saved your life and that all five of you stabbed her in the back because you saw me in the future."

Her face drained. "We didn't-"

She cut off as a tall, board man came to a halt behind her. My eyes flicked up to meet his, and I froze.

"Front of the cabin," Lord Zeus instructed, his eyes narrowed. "Now."
"What?" Olympia frowned. "She isn't going anywhere!"

"Hey!" I hissed, elbowing her quick as my father's eyes flashed angrily.

She only glowered back at me. "I am not let you go anywhere with strange men, Ace!"

One of my father's eyebrows rose, and for some unfathomable reason, I felt my cheeks flush in embarrassment. I cleared my throat. "That's Lord Zeus. My father."

Olympia's face fell in shock and behind Zeus, Nick cursed under his breath, hiding his face behind his hand. Sighing heavily, I pushed myself to my feet and skirted past her to follow my father to the front of the plane.

"Sorry," I grumbled. "I didn't realise that she had no idea-"

"Sit down," he interrupted, pointing at the far seat beside the window. I cut off, gulping hard and moving to do as he said. Setting his jaw, he sat down beside me. "Do you know why I'm here?"

I shifted, my stomach churning nervously. "Erm, no?"

By the look on his face, that wasn't the right answer. "You told me that under no circumstances would you ever complete the tasks the Olympians set out for you," he told me in monotone. My chest tightened. "I returned to Olympus and warned them that if any of them should try and ignore your request, they'd spend the next millennia in Tartarus."

I gulped hard. "That sounds… drastic."

He ignored me. "Now I find that, despite my best efforts to convince you not to give up your life, it took the interference of Apollo to make you agree."

"That's not fair," I rushed before I could stop myself. He glowered at me. "Artemis was the one that sent me to find the others, and there was no way Apollo would have given me the information I needed if I hadn't agreed to do it. It wasn't exactly my first choice!"

A fraction of his anger faded, but not much. "Did it ever occur to you to do exactly what every other demigod does and ask your father? Even Perseus Jackson knows Poseidon would help him if it was ever possible."

I hesitated. "But… that's interference… isn't it?"

"Don't treat me like a fool, Acacia," Zeus scoffed. "I know very well that the gods bend that rule as much as they can get away with." He shot me a look. "It's only interference if you get caught."

My jaw must have dropped, because he was glowering at me again. "You're the god of law and order!" I breathed.

"I'm aware," he scowled stiffly. "And you are my daughter."

That strange feeling stirred in my chest again. It was one I didn't get very often, and one only Zeus's words could cause – the feeling that maybe, just maybe at least one of my parents hadn't completely disregarded me all those years ago.

I gulped hard again. "I'm sorry," I said sincerely. "I wasn't thinking."
"That seems a common theme where Apollo is concerned," he grumbled. My cheeks flushed again. "Complete the tests if you must. But I will not grant you immortality just to see that Sun God torment you for eternity."

"The other gods won't like that," I pointed out quietly.

"I wasn't asking them," he dismissed easily. I glanced at him, failing to stop a small smile tugging at the side of my lips. "Your sister is in Las Vegas."

The mention of Thalia made the smile fade, and worry erupted in the pit of my stomach. "Is she okay?"

Zeus frowned. "For now. She and the Jackson boy need to tread carefully."

"So Percy did find them," I sighed, a little more relieved. As terrible as the two of them could be together, I had to believe that they could work together, for Annabeth if no one else.

My eyes drifted back to Zeus. "There's another child of the Big Three out there," I commented. He lifted an eyebrow again. "Demetria King. The daughter of Hades."

Immediately, his expression darkened. "She's old enough to be no significant threat," he dismissed in disgust.

"But you don't like her?"

"I don't much like Perseus Jackson either."

"This is different. Demetria's working with Luke, she's dangerous."

"So is Perseus Jackson."
I couldn't help groaning. "Because he's Poseidon's son? Well I guess that means I am too!" His jaw locked. "Look, I don't know what's she up to, but I have to stop her. She's going to keep coming after me until one of us is dead, and last I looked, Percy was the polar opposite. Didn't the children of Zeus and Poseidon work together to defeat the children of Hades last time?" There was a flicker of recognition in his eyes. "I trust Percy with my life. Demetria's another story."

For a moment, Zeus only stared straight ahead, debating his answer. "Find out what she wants and why she is after you," he instructed. "You're going to have to complete those tests now, so the moment I leave here, the Olympians are fully within their rights to approach you again. That includes Apollo, so be careful."

My stomach twisted. "I know."

He pushed himself to his feet. "Good luck, Acacia." I nodded, watching him turn to stride back down the plane.

After a moment, I stood and moved back down to my seat beside Olympia. She and Nick both stared expectantly. "Shouldn't you have already seen this?" I commented dryly at Olympia.

Her eyes narrowed. "It's annoyingly selective sometimes. Are you going to explain or just try your best to annoy me?"

"Makes a nice change," I scoffed. Her arms folded moodily. "When you don't play along, it's not as fun."

"Amen," Nick snorted.

"You, keep quiet!" Olympia ordered her brother. "You," she continued, pointing at me. "Start talking."

A burst of anger shot through me. "Me?" I glowered. "What about the two of you? Who the hell is Demetria King and why does she want me dead?"

Olympia's face fell and Nick dropped his head again. For a long minute, they simply sat in silence, debating their answer like their lives depended upon it. "I… erm…" For once, Olympia looked lost for words.

Nick locked his jaw. "She deserves to know."

Pity flashed across his sister's face. "You don't have to be here," she said softly. "I'm sure Ace won't mind if you-"

"Oly, stop," he warned, his voice dangerously level. I blinked in surprise, a little taken aback by just how much he reminded me of Apollo when he got upset.

"Nick," she sighed, still looking sorry for him.

If anything, that only made him angrier. His face set and he met my stunned look without flinching. "Demetria King is my fiancée."