He used to stand over her bed offering smart, surprising tips on her homework. Now he wouldn’t even step into her room.

He nodded toward her book. “The uncertainty principle? Tough one. The more you know about how one variable changes, the less you know about the other. And everything is changing all the time.”

Eureka looked at the ceiling. “I don’t know the difference between variables and constants anymore.”

“We’re only trying to do what’s best for you, Reka.”

She didn’t answer. She had nothing to say to that, to him.

When he closed the door, she read the paragraph introducing the uncertainty principle. The chapter’s title page featured a large triangle, the Greek symbol for change, delta. It was the same shape as the gauze-wrapped thunderstone.

She pushed aside her book and opened the box. The thunderstone, still wrapped in its odd white gauze, looked small and unassuming. She picked it up, remembering how delicately Brooks had handled it. She tried to achieve the same level of reverence. She thought about Ander’s warning that she must test the stone alone, that Brooks was not to know what she had. What did she have? She’d never even seen what the stone looked like. She thought of Diana’s postscript:

Don’t unwrap the gauze until you need to. You’ll know when the time comes.

Eureka’s life was in chaos. She was on the brink of being kicked out of the house she hated living in. She hadn’t been going to school. She was alienated from all her friends and was following birds through the predawn bayou to meet elderly psychics. How was she supposed to know if now was Diana’s mystical when?

As she reached for the glass on her nightstand, she kept the stone in its gauze. She placed it on top of her Latin binder. Very carefully, she poured a small stream of last night’s water directly over the stone. She watched the wet spot seeping through gauze. It was just a rock.

She put the stone down and kicked her legs out across the bed. The dreamer in her was disappointed.

Then, in her peripheral vision, she saw the smallest movement. The stone’s gauze had lifted in one corner, as if loosened by the water. You’ll know when. She heard Diana’s voice as if she were lying next to Eureka. It made her shiver.

She peeled back more of the corner of the gauze. This sent the stone spinning, shedding layer after layer of white wrapping. Eureka’s fingers sifted through the loosening fabric as the triangular shape of the stone shrank and sharpened in her hands.

At last the final layer of gauze fell away. She held in her hands an isosceles-sided stone about the size of the lapis lazuli locket, but several times heavier. She studied its surface—smooth, with some crags and imperfections, like any other rock. It was shot through here and there with grainy blue-gray crystals. It would have made a good skipping stone for Ander.

Eureka’s phone buzzed on her nightstand. She lunged for it, inexplicably certain it would be him. But it was coquettish, half-dressed Cat’s photo on her phone’s display. Eureka let it go to voice mail. Cat had been texting and calling every few hours since first period that morning. Eureka didn’t know what to tell her. They knew each other too well for her to lie and say nothing was going on.

When her phone faded to black and her bedroom was dim again, Eureka became aware of a faint blue light emanating from the stone. Tiny blue-gray veins glowed along the surface of the rock. She stared at them until they began to resemble the abstractions of a language. She turned the stone over and watched a familiar shape form on the back. The veins were making circles. Her ears rang. Goose bumps blanketed her skin. The image on the thunderstone looked precisely like the scar on Brooks’s forehead.

A faint crack of thunder sounded in the sky. It was only a coincidence, but it startled her. The stone slipped from her fingers and slid into a recess of her comforter. She reached for the glass again and poured its contents onto the bare thunderstone like she was putting out a fire, like she was extinguishing her friendship with Brooks.

Water splashed back from the stone and hit her in the face.

She spat and wiped her brow. She gazed down at the stone. Her bedspread was wet, her notes and textbooks, too. She blotted them with a pillow and moved them aside. She picked up the stone. It was as dry as a cow’s skull on a juke-joint wall.

“No way,” she muttered.

She slid off the bed, carrying the stone, and cracked open her door. The TV downstairs was tuned to local news. The twins’ night-light cast feeble rays through the open door of the room they shared. She tiptoed to the bathroom, shut and locked the door. She stood with her back against the wall and looked at herself holding the stone in the mirror.

Her pajamas were splattered with water. The edges of the hair framing her face were wet. She held the stone under the faucet and turned the water on all the way.

When the stream hit the stone, it was instantly repelled. No, that wasn’t it—Eureka looked closer and saw that the water never even hit the stone. It was repelled in the air above and around it.

She turned off the tap. She sat on the lip of the copper baignoire tub, which was crammed with the twins’ bath toys. The sink, the mirror, the rug—all were soaking wet. The thunderstone was absolutely dry.

“Mom,” she murmured, “what have you gotten me into?”

She held the stone close to her face and examined it, turning it over in her hands. A small hole had been made at the top of the triangle’s widest angle, large enough for a chain to slip through. The thunderstone could be worn as a necklace.

Then why keep it wrapped in gauze? Maybe the gauze protected whatever sealant had been added to repel water. Eureka looked out the bathroom window at the rain falling on darkened branches. She got an idea.

She dragged a towel across the sink and floor, trying to mop up as much water as she could. She slipped the thunderstone into her pajama pocket and crept down the hall. At the head of the stairs she looked down and saw Dad asleep on the couch, his body lit up by the glow of the TV. A bowl of popcorn was balanced on his chest. She heard frantic typing coming from the kitchen that could only be Rhoda torturing her laptop.

Eureka stole down the stairs and gently opened the back door. The only one who saw her was Squat, who came trotting out with her because he loved to get muddy in the rain. Eureka scratched his head and let him jump up to kiss her face, a habit Rhoda had been working on breaking him of for years. He followed Eureka as she moved down the porch stairs and headed for the back gate to the bayou.

Another crack of thunder forced Eureka to remind herself that it had been raining all evening, that she’d just heard Cokie Faucheux say something on TV about a storm. She raised the latch on the gate and stepped onto the dock where their neighbors slipped their fishing pirogue into the water. She sat down at the edge, rolled up her pajama legs, and sank her feet into the bayou. It was so cold her body stiffened. But she left her icy feet there, even as they started to burn.

With her left hand, she pulled the stone from her pocket and watched thin raindrops ricochet off its surface. They drew Squat’s bewildered attention as he sniffed the stone and got water up his nose.

She made a fist around the thunderstone and plunged it into bayou, leaning over and straightening her arm in the water, inhaling sharply from the cold. The water shuddered; then its level rose, and Eureka saw that a large bubble of air had formed around the thunderstone and her arm. The bubble ended just below the surface of the water, where her elbow was.

With her right hand, Eureka explored the underwater bubble, expecting it to pop. It didn’t. It was malleable and strong, like an indestructible balloon. When she pulled her wet right hand from the water, she could feel a difference. Her left hand, still underwater, encased by the pocket of air, wasn’t wet at all. Finally, she pulled the thunderstone out of the water and saw that it, too, had remained absolutely dry.

“Okay, Ander,” she said. “You win.”

24

THE DISAPPEARANCE

Tap. Tap. Tap.

When Polaris arrived at her window before sunrise Tuesday morning, Eureka was out of bed by the third tap on the glass. She parted her curtains and slid the cold pane up to greet the lime-green bird.

The bird meant Blavatsky, and Blavatsky meant answers. Translating The Book of Love had become Eureka’s most compelling mission since Diana died. Somehow, as the tale grew wilder and more fanciful, Eureka’s connection to it cemented. She felt a childlike curiosity to know the details of the gossipwitches’ prophecy, as if it bore some relevance to her own life. She could hardly wait to meet the old woman down at the willow tree.

She’d slept with the thunderstone on the same chain as the lapis lazuli locket. She couldn’t bear to wrap it up and stow it away again. It was heavy around her neck, warm from lying against her chest all night. She decided to ask Madame Blavatsky’s opinion on it. It meant welcoming the old woman deeper into her private life, but Eureka trusted her own instincts. Maybe Blavatsky would know something that would help Eureka better understand the stone—maybe she could even explain Ander’s interest in it.

Eureka held out her hand to Polaris, but the bird flew past her. He swooped inside her room, flew in an agitated circle near the ceiling, then darted back out the window into the charcoal sky. He flapped his wings, sending a draft of pine-scented air Eureka’s way, exposing the variegated feathers where his inner wings met his breastbone. His beak widened skyward in a shrill squawk.

“Now you’re a rooster?” she said.

Polaris squawked again. The sound was wretched, nothing like the melodic notes she’d heard him trill before.

“I’m coming.” Eureka looked at her pajamas and bare feet. It was cold outside, the air moist and the sun a long way off. She grabbed the first thing her hands found in her closet: the faded green Evangeline tracksuit she used to wear to cross-country away meets. The nylon suit was warm and she could run in it, and there was no reason to be sentimental about the team she’d had to beg to quit. She brushed her teeth and whipped her hair into a braid. She met Polaris by the rosemary bush at the edge of the front porch.

The morning was wet, filled with the gossip of crickets and the clean whisper of rosemary swaying in the wind. This time, Polaris didn’t wait for Eureka to tie her running shoes. He flew in the same direction she’d followed him the other day, but faster. Eureka started to jog. Her eyes were somewhere between groggy and alert. Her calves burned from yesterday’s run.

The bird’s squawk was persistent, abrasive against the dormant street at five in the morning. Eureka wished she knew how to quiet him. Something was different about his mood today, but she didn’t speak his language. All she could do was keep up.

She was sprinting when she passed the paperboy’s red truck at the end of Shady Circle. She waved as if she were friendly, then turned right to cut through the Guillots’ lawn. She reached the bayou, with its army-green morning glow. She’d lost sight of Polaris, but she knew the way to the willow tree.

She could have run it with her eyes closed, and it almost seemed as if she did. Days had passed since Eureka had slept well. Her tank was nearly empty. She watched the moon’s reflection shimmering on the surface of the water and imagined it had spawned a dozen baby moons. The infant crescents swam upstream, leaping like flying fish, trying to outpace Eureka. Her legs pumped faster, wanting to win, until she stumbled over the woody roots of a fern and tumbled into the mud. She landed on her bad wrist. She winced as she regained her footing and her pace.