“Don’t worry, William,” Claire told her brother, who was older by nine minutes. “I’m magic.”

“I know.” William sat cross-legged in Cat’s lap on the translucent floor of the shield, picking pills off his pajamas. Beneath them, the sea built hills and valleys of debris. Black strands of algae slapped like shaggy beards against the shield. Branches of coral jostled its sides.

Cat hugged William’s shoulders. Eureka’s friend was smart and audacious—together they had hitchhiked to New Orleans, Cat wearing only a bikini top and cutoffs, singing raunchy Navy songs her dad had taught her. Eureka could tell Cat thought the plan with Claire was a bad idea.

“She’s just a kid,” Cat said.

“There.” Ander pointed to a broad, barnacle-covered slab of stone ten feet overhead. “That one.”

White foam sparkled beneath its crevices. The stone’s surface was above water.

Eureka’s arm joined Ander’s in propelling the shield higher. The water changed from black to dark gray. When they were as close as they could get without breaking the surface, Eureka clasped her thunderstone and sent a prayer Diana’s way that they make it out safely.

Though only Eureka could erect the shield they traveled in, Ander could maintain it for a while. He would be the last to leave.

He studied Eureka. She glanced down, wondering what she looked like to him. The intensity of his gaze had made her nervous when she first encountered him on the road outside New Iberia. Then last night he told her he’d been watching her for years, since both of them were very young. He’d betrayed everything he was raised to believe about her. He said he loved her.

“When we get above the ocean,” he said, “we will see terrible things. You must prepare yourself.”

Eureka nodded. She had felt the weight of her tears as they left her eyes. She knew her flood was more horrible than any nightmare. She was responsible for whatever lurked above, and she planned on redeeming herself.

Ander unzipped his backpack and withdrew what looked like an eight-inch silver stake with a wedding-band-sized ring at the top. He flicked a switch to release four curved flukes from the stake’s base, transforming it into an anchor. When he pulled on the ring, a fine chain of silver links spurted from the top.

Eureka touched the strange anchor, amazed by its lightness. It weighed less than half a pound.

“Pretty.” William touched the anchor’s sparkling flukes, which were forked at the edges and had a scalelike hammered texture that made them look like little mermaid tails.

“It is made of orichalcum,” Ander said, “an ancient substance mined in Atlantis, stronger than anything in the Waking World. When my ancestor Leander left Atlantis, he had five pieces of orichalcum with him. My family has held on to them formillennia.” He patted his backpack and managed a mysterious, sexy smile. “Until now.”

“What are the other toys?” Claire stood on her toes and stuffed a hand into Ander’s backpack.

He hoisted her in his arms and smiled as he zipped his bag up. He placed the anchor in her hands. “This is very precious. Once the anchor grips the rock, you must hold on to the chain as tightly as you can.”

The links of orichalcum jangled in Claire’s hands. “I’ll hold tight.”

“Claire—” Eureka’s fingers brushed her sister’s hair, needing to convey that this wasn’t a game. She thought about what Diana would have said. “I think you’re very brave.”

Claire smiled. “Brave and magic?”

Eureka willed away the strange new urge to cry. “Brave and magic.”

Ander lifted Claire over his head. She planted her feet on his shoulders and plunged one fist up, then another, just as he’d instructed. Her fingers passed through the thunderstone shield and she flung the anchor toward the rock. Eureka watched it sail upward and disappear. Then the chain grew taut and the shield shook like a cobweb hit by a sprinkler. But it did not let in water, and it did not break.

Ander tugged the chain. “Perfect.”

He pulled, drawing more chain inside the shield, lifting them closer to the surface. When they were only inches below the crashing waves, Ander shouted, “Go!”

Eureka grabbed the chain’s smooth, cold links. She reached past Claire and began to climb.

Her agility surprised her. Adrenaline flowed through her arms like a river. When she crossed the shield’s border, the surface of the ocean was just above her. Eureka entered her storm.

It was deafening. It was everything. It was a voyage into her broken heart. Every sadness, every ounce of anger she had ever felt manifested in that rain. It stung her body like bullets from a thousand futile wars. She gritted her teeth and tasted salt.

Wind slashed from the east. Eureka’s fingers slipped, then clung to the cold chain as she reached for the rock.

“Hold on, Claire!” she tried to shout to her sister, but her mouth filled with salt water. She buried her chin against her chest and pressed upward, onward, urgent with a determination she’d never known before.

“Is this all you can do?” she shouted, gurgling through her torrential pain.

The air smelled like it had been electrocuted. Eureka couldn’t see beyond the deluge, but she sensed that there was only flood to see. How could Claire hold on in all this thrashing water? Eureka envisioned the dispersal of the last people she loved across the ocean, fish nibbling their eyes. Her throat constricted. She slipped essential inches down the chain. She was up to her chest in ocean.