Charleston University’s Department of Geology and Environmental Sciences was eight blocks away, on Coming Street.

We drove past Ella’s house on the way. It was all I could do not to cry.

Ben found a spot out front. We entered a three-story brick building and took the elevator up one floor. Stepping into a small lobby, we asked a passing student for the office of Professor Wiley Marzec.

Marzec was younger than I’d expected—no more than forty. A bit thick around the middle, with a round, friendly face and a mullet of brown hair. He wore lime-green shorts and a brown T-shirt that said “Rocktastic.” When he spoke, his voice filled the room.

“Come in, come in!” Half rising, Marzec waved to a pair of wicker chairs facing his desk. His office was small, but cozy, lined with wooden bookshelves holding an assortment of stones, fossils, and thick textbooks. Something called the International Stratigraphic Chart was taped to one wall. A fantastic geode rode his desk as a paperweight.

“Cool!” Hi zoomed to the sparkling rock.

“I know, right?” Marzec waved permission for Hi to touch it. “It’s amethyst, which is the purple version of quartz. And check out that red streak circling the core. That’s pure hematite under the crystalline surface. Found it at Thunder Bay, up in Canada. All the other rock-jocks are jealous.”

“Dope.” Wisely, Hi didn’t attempt to pick it up. “Five bucks?”

“Not on your life.” Marzec smiled as he turned to me. “Tory, I presume?”

“Yessir.” Slipping into a seat. “And thank you so much for seeing us on short notice.”

“My father’s name was Sir.” Wiley leaned back in his creaky office chair. “I’m Wiley. Or Professor Marzec, if you must. Now, what can I do you for?”

“We found a rock that seemed out of place.” I snapped for Shelton, who was standing behind me. Hi had filled the other seat, with Ben looming over his shoulder. “We were hoping you could tell us what it is.”

Shelton handed me the ziplock. Hesitating only slightly, I passed it to Marzec.

“Ah!” Marzec smiled wide. “A phosphate nodule. Were you guys down by the river?” His fingers found the bag’s seal. “May I?”

“I’d prefer you didn’t,” I said quickly.

Marzec’s brows quirked, but he set the bag on the desk and peered through the plastic.

“You said something about a river?” Hi prompted. “Which one?”

Marzec’s whole focus was on the stone. “Copper. Wando. Edisto. Any of them. But I was mainly thinking of the Ashley.” He sat back. “What do you know about phosphate mining in the Lowcountry?”

Our blank faces gave him his answer.

Marzec glanced at the ceiling in thought. “Where to start?”

“How about the Cliff Notes version?” I suggested.

“Sounds good.” Marzec tapped the plastic bag. “What you have is called a phosphate nodule. A real beauty, too, must weight five pounds. Can’t you smell that odor? These rocks are found throughout the Charleston Basin, and along the banks of the tributary rivers. Their ages range from the Oligocene to the Pleistocene epochs. In South Carolina, phosphate deposits run parallel to the coast for about seventy miles, extending south from the Wando to the Broad River, and then inland for approximately thirty miles.”

My heart sank. That sounded like a lot of real estate.

“What exactly is phosphate?” Shelton asked.

“Let’s start with phosphorus.” Marzec’s voice became professorial. “One of the seventeen nutrients required by all living plants and animals, it’s absolutely crucial for growing food. If the dirt you’re farming lacks phosphorus, that deficiency will severely limit production. To compensate, farmers use various fertilizers to correct any shortfall and increase crop yields.”

“Soil needs phosphorous to grow crops,” I summarized. “Got it.”

“Exactly. Phosphorus is essential to life—there’s no substitute for it in agriculture. The element readily combines in nature, forming crucial organic compounds. For example, it’s a vital component of nucleic acids—DNA and RNA molecules—from which all life springs. It’s also a key component of phospholipids, plasma membranes, and solid structures like bones and teeth.”

“Need phosphorus to live,” Hi said. “Roger that.”

Marzec winked, perhaps acknowledging his long-winded style. “I’ll cut to the chase—phosphorus itself is highly reactive, and doesn’t appear naturally in its elemental form. Instead, it occurs in phosphates—charged groups of atoms. Basically, a phosphorus atom hooked to four oxygen atoms.”

“Okay.” This was getting more technical than I’d expected.

“You can’t mine pure phosphorus,” Marzec simplified. “It doesn’t exist anywhere. Instead, you have to look for phosphate rocks—like this one—dig them up, then break the stones down.”

“Okay.” I shifted, not totally sure I understood. “Phosphate rocks contain phosphorus, which is essential for making good fertilizer. So people dig them up for sale.”

“Perfectly stated.” Marzec spread his hands. “This was a major industry in the late 1800s. The amount of available farmland was limited, which meant the same tired plots had to be replanted over and over. Overuse was leaching essential nutrients from the soil. Farmers were desperate for a way to get those minerals back. Enter phosphate mining.”

“They needed prehistoric rocks to make fertilizer?” Hi asked. “Nothing else worked?”

“Before the mining boom, farmers were dependent on guano for fertilizer. But that had to be imported, and was very pricey. Finding high-quality fertilizer buried right beneath their feet was a godsend for local sharecroppers.”

“Wait. Guano?” Hiram’s eyes narrowed. “You’re saying—”

“Yes.” Marzec grinned. “Farmers were buying the droppings of seabirds and bats, which are high in both phosphorus and nitrogen.”

Shelton crinkled his nose. “Man, farming is just nasty. For real.”

“Are phosphate rocks widespread?” I asked.

“Actually, no.” Marzec jabbed a thumb at a multicolored map behind his desk. “There are large deposits in central Florida, certain regions of Idaho, and along the North Carolina coast. Smaller ones in Montana, Tennessee, and, of course, here in the Lowcountry. Phosphate rock was so prevalent along the Ashley River that many landmarks in that area still bear its name.”

“Ashley Phosphate Road,” Ben said. “I’ve driven there.”

“Correct.” Marzec stroked his chin. “The banks of the Ashley River were riddled with phosphates. Once their utility was discovered, mining companies sprang up along the waterfront. For the next fifty years, strip mining for phosphate rock was the major industry in that area. By 1885, South Carolina was producing half the world’s supply. Some folks got rich, although Mother Nature won’t be sending them any thank-you cards. Entire sedimentary layers were dug up, ripped out, and then barged downstream.”

There was a pause as Marzec seemed to run out of steam.

“Is phosphate mining still a big business today?” I prompted.

“Oh no.” Marzec took a long pull on a Diet Coke. “Most of the local deposits quickly tapped out. By the 1900s, the vast majority of operations had shuttered. Fertilizer production had all but ceased in these parts by the 1930s.”

I shifted again, thinking hard. “So are these phosphate sediments still prevalent near the riverbanks?”

“I wouldn’t say prevalent.” He tapped the bag once more. “Honestly, I’m surprised you found a pure nodule of this size just lying around.” Marzec eyed me curiously. “Where did you pick this up?”

“Wake-boarding off Folly Beach,” Hi inserted. “I was attempting a heel-side five-forty when I wiped out. Found this little guy bouncing in the surf.”

“I see.” I could tell Marzec was skeptical, but he let it pass. “Well, any other questions?”

“No, Dr. Marzec.” I flashed my very-grateful smile. “Thanks so much for your time.”

“Delighted.” Marzec scratched behind his ear with a snort. “I’ve been working here five years, and you’re the first non-students to ever ask me a thing. Come back anytime.”

We gathered our things, Hi gently scooping the rock from Marzec’s desk, then exited with another round of thanks. I waited until we were safely inside Ben’s SUV before speaking.

“What do you guys think? Marzec kept mentioning the Ashley River.”

“But these rocks were everywhere,” Hi said. “He listed every other river in the area, too.”

Shelton shook his head. “We could maybe narrow our search to locations near a riverbank. But that’s still miles and miles. And for all we know, the kidnapper just picked up the stupid rock while out driving around. It might not lead to anything.”

I looked at Ben. He glanced away.

No one wanted to say it straight out.

“So we’re still nowhere.” My voice trembled slightly.

Silence filled the car.

I could sense the boys wanted to comfort me. Had no idea how to.

“Let’s go home,” I said softly.

• • •

“Tory, where have you been?”

There was real concern in Kit’s voice as he sprang up from the couch.

I elected for half truth. “The boys and I went to where Ella worked. I thought maybe we could spot something.”

“Oh, honey.” He wrapped an arm around my shoulder.

I felt tears welling behind my eyes. Forced them back.

Kit released me. Held me at arm’s length so he could look into my eyes.

“If you want to cancel this barbeque, just say the word. Whitney will be fine.”

The block party. I’d completely forgotten.

Of course we can’t have a stupid cookout today. My friend was abducted!

“It’s fine.” A glance at the clock. “Tell Whitney I’ll be ready to help in an hour. Where’s Coop?”

“He’s asleep on your bed.” Kit ran nervous fingers through his curly brown hair. “Are you sure, kiddo? I don’t know if this party is a good idea.”

“It’s okay. Better a dumb cookout than nothing. Maybe it’ll keep my mind off . . . things.”

Kit nodded slowly. “Only if you’re certain. And we leave the minute you want to.”

I forced a smile. “Thanks, Dad.”

He tried to hide his surprise. I never called him that.

Then I saw today’s Post and Courier sitting on our dining room table.

I started. “What is that!?”

Kit tracked my eyes, then winced. “There’s a story. Maybe now’s not the best—”

Ignoring him, I grabbed the newspaper. A giant picture dominated above the fold.

Two playing cards, side by side. Ophiuchus. Cetus.

A banner headline screamed: “Zodiac Kidnapper Baffles Police.”

Eyes wide, I read the full-page story. Then I slammed the paper on the table.

“The police don’t know anything!” Sides heaving. “But the press has it all the next day!”

Kit grabbed the newsprint and dumped it in the recycling bin. “Forget that nonsense. I’m sure the police have leads they aren’t sharing.”

I shook my head angrily. “Someone has leaked every major development in these cases so far. Yet the cops don’t have a damn clue.”

“Tory, I understand how upset you are, but we have to trust—”

“I know more than those bozos!”

Kit stopped short. “I’m sorry?”

Careful!

I buried my face in my hands. Worry for Ella was compromising my judgment.

Then I made a decision.

“Kit?”

“Yeah, kiddo?” Watching me closely.

“Please sit with me. I have some things to tell you.”

We each pulled a chair from the dining table. Sat facing each other.

Deep breath.

It’s the right thing to do.

“We need to visit police headquarters. Today. I have evidence they need to see.”