I DIDN’T UNROLL the map that evening.

Too wiped out. After the day’s drama, treasure hunting went on hold. I conked out minutes after unlocking my front door.

We gathered the next morning in Shelton’s garage. Nelson Devers, LIRI’s tech director, had converted the small space into a computer repair station. Metal shelves lined the walls, jammed with plastic containers full of bolts, screws, circuit boards, and other mechanical bits. Fluorescent lights hung from the ceiling. A large drafting table, the primary workspace, occupied the center of the floor.

“Time to work.” Switching on a handheld magnifier, I unfurled our stolen prize.

The treasure map was weathered and cracked, but well preserved. The paper had dulled to the color of Dijon mustard, and smelled of dust, must, and age.

Faded script flowed across the document’s top and bottom. At center, intersecting lines formed a vague image of some sort.

“Huh.” Hi scratched his chubby chin. “Hmmm.”

“What the frick?” I’d expected mountains, valleys, maybe a shoreline or rock formation. Some identifiable feature. Instead, I was seeing a confounding muddle of straight and squiggly lines, surrounded by a simple black border.

“Who drew this?” Shelton complained. “Monet? Picasso?”

“Three vertical lines, and seven or eight horizontal.” I frowned. “Then you’ve got this thick streak running from top to bottom, beneath the jumble.”

There was no recognizable topography or geography. Not even a directional indicator. The sketch looked like a child’s drawing, or superimposed games of tic-tac-toe.

“That’s a map?” Ben scowled. “Looks like a scribble of random lines.”

“Underwhelming,” I admitted.

“Focus on the writing,” Hi said. “The words might explain the drawing.”

A two-line stanza crossed the top of the map in bold, graceful calligraphy. Focusing the magnifier, I read aloud:

Down, down from Lady Peregrine’s roost,

Begin thy winding to the dark chamber’s sluice.

“A riddle?” I couldn’t believe it. “Seriously?”

The cryptic verse shed no light on the chicken-scratch design.

“Read the bottom,” Hi said. “Maybe the poem makes sense in combination.”

I ran the lens over the second verse. Same aggressive handwriting. New unfathomable message:

Spin Savior’s Loop in chasm’s open niche,

Choose thy faithful servant to release correct bridge.

“Not very helpful.” A classic Hi understatement.

“Is that supposed to rhyme?” Shelton sounded unimpressed.

He got no answer.

I searched, but found no more writing.

No wonder museum security was lax, I thought. Without context, the map was useless.

“This could be a diagram of underground tunnels,” I said, gesturing at the mishmash in the center, “or possibly caves.”

“Maybe a coastline?” Hi ventured. “But it doesn’t say what island.”

“That mess could be anything,” Shelton muttered. “We don’t even know this is an island.”

“All the rumors point to an island.” Hi yanked a wad of folded papers from the back pocket of his shorts. “I spent hours online. Seabrook. Johns. Fripp. Some fishermen think the references point to Kiawah. But everyone agrees—Bonny buried her treasure on a barrier isle.”

“No one’s found it,” Ben countered. “So the popular theories must be wrong.”

“Don’t shoot the messenger,” Hi replied. “Other than those theories and this map, we’ve got squadoosh.”

Having nothing to add, I kept scouring the map for further clues.

A symbol decorated the lower left corner. I leaned closer to inspect it.

It was a green and silver cross. Tall. Thin. Oddly shaped, with the upper tine curving sharply to the right. A circle ringed the intersection of the vertical and horizontal arms.

The odd little emblem held my eye. I’d never seen anything like it. The cross was beautiful, and drawn with care. But it told me nothing.

“Let’s brainstorm,” I said. “What do we know about Anne Bonny?”

“She was ballsy,” Shelton said. “She liked to disguise herself as a man and slip into Charles Town. Even with a bounty on her head.”

“Women be shoppin’,” Hi said matter-of-factly. “Can’t stop ’em.”

I ignored him. “So Anne would just stroll around downtown? In the open?”

Shelton nodded. “My pirate book says Bonny owned a small boat. She kept it outside the harbor and used it to sneak ashore.”

“A fellow skipper,” Ben said. “I like her more already. What’d she name her vessel?”

“Hold on.” Shelton disappeared into his house, returned shortly with a battered hardback. “Her boat was named Duck Hawk.”

Something clicked. “Duck Hawk?”

Shelton nodded.

I reread the map’s first line. “Down, down from Lady Peregrine’s roost.”

“I think this sentence tells you where to start.” Excited, I tapped the words. “Directions to the tunnel entrance, or whatever the thick streak on the map is. We should be looking for Lady Peregrine’s roost.”

“Old news,” Hi said. “That’s why people suspected the islands I mentioned. In the early 1700s, both Seabrook and Kiawah had peregrine falcon colonies.”

“Treasure hunters dug beneath every falcon nest in the state,” Ben added. “Found jack squat.”

I ignored them. My mind was connecting dots. “Isn’t ‘duck hawk’ another name for falcon?”

“That’s true.” Shelton pursed his lips in thought. “You think the poem’s talking about her boat? But where would Anne Bonny’s boat go to roost?”

“No.” I held up a hand. “You missed a link. The rhyme mentions a ‘Lady Peregrine.’ That could mean ‘girl falcon.’ The girl falcon, actually, since the words are capitalized.”

Shelton squinted. “I don’t follow.”

“Anne Bonny named her boat Duck Hawk. She could be the girl falcon. Anne Bonny might be Lady Peregrine!”

“So we should be looking for Anne Bonny’s roost.” Hi got it.

“Which makes no sense,” said Ben.

“Wait,” I said. “Give me a second to think.”

They did.

“When Bonny snuck into town,” I asked, “where did she park Duck Hawk? Didn’t the town watch patrol the docks?”

“Not all of them,” Shelton said. “There must’ve been a few piers she could’ve used to stay under the radar.”

“Can we find out?”

“Sure.” Shelton began flipping pages in his book.

“What are you thinking?” Ben asked.

“Bonny liked to hide in plain sight, right?”

“Right.”

“Why not bury your treasure in plain sight as well?”

Hi’s brow furrowed. “You think she stashed her loot somewhere downtown? Inside old Charles Town? That’s new, I’ll give you that much.”

“So,” Ben said slowly, “you’re saying that ‘Lady Peregrine’s roost’ could describe where Anne Bonny would dock Duck Hawk?”

“It’s just a theory.”

“Got it!” Shelton’s finger jabbed a page. “According to the author, Bonny used the docks on East Bay Street. They allowed for a quick getaway if needed.”

“Huh.” Hi rolled back on his heels, examined the ceiling.

“What, Hi?” I hated having to drag things out of him.

“Well …” Hi hesitated. “Sea caves.”

Impatient, I almost tapped a foot. “Care to elaborate?”

Hi turned to Shelton. “Does this room get Wi-Fi?”

“Yeah, why?”

“Back in a jiff.”

Hi headed toward his townhouse.

Several minutes passed.

“If he’s making a burrito,” Ben growled, “I’ll pound him.”

“Now, now.” Hi walked in carrying his laptop. “Patience! Dr. Hiram is going to blow your mind.”

“Get on with it,” Shelton grumbled.

“East Bay Street runs along the eastern edge of the peninsula, yes?” Hi adopted a professorial tone. “That shoreline is riddled with sea caves, some leading under the city streets.”

“How would you know that?” Ben. Skeptical.

“Because I do,” Hi said primly. “My uncle’s a city planner, and I like maps.”

Hi tapped a few keys, then flipped his laptop around, displaying a geological map of Charleston. The left side of the peninsula was dotted with tiny indentations.

Another mental click. “Oh my.”

Six eyes rolled to me.

“Peregrine falcons nest in sea caves,” I said. “In other words, they roost in them.”

“So?” Ben said.

“Anne Bonny would dock Duck Hawk near the East Bay sea caves.”

“Ah.” Shelton said. Ben still looked lost.

“Bonny’s falcon-named boat would ‘roost’—” air quotes, “—on East Bay Street.” I let the idea sink in. “We should be looking downtown.”

“Which is why I got my computer,” Hi said. “Watch.”

Whipping out his iPhone, Hi snapped a shot of the treasure map.

“Step one.”

He downloaded the image to his laptop.

“Step two.”

“You’re such a dork,” Shelton snickered.

Hi waggled a finger. “Do not interrupt a master at work. Step three.”

Opening Firefox, Hi pulled up a satellite map of Charleston. Then he double-clicked the treasure-map image and set them side by side.

“I see.” Shelton adjusted his glasses. “I can do better, if you let me.”

“I was wondering how long it’d take you.” Hi stepped aside. “Have at, hack master.”

My gaze flicked between the two. “I still don’t have a clue what you’re doing.”

“Hi had a good idea,” Shelton said. “For once. I’m gonna wash out the treasure map image so only the lines remain. Then we can superimpose it over the satellite photo and see if the configuration matches anything.”

Clickity click. “The straight lines on the map. Could they be streets?”

“Nice!” Shelton opened a new browser. “Let’s check them against a map of old Charles Town.”

A million cyber loops later, Shelton had located a city diagram dated 1756.

“Close enough,” he said.

For the next few minutes we looked for corresponding patterns. It was like searching for a needle in a stack of needles.

Finally, Hi spotted a semi-match.

“Check that out!” His voice cracked. “These two straight lines track pretty well over East Bay and Church streets. I think we may have something!”

“That’s straight CSI right there.” Shelton fist-bumped Hi, and both exploded it backward. Tools.

Ben snorted. “There’s no way pirate treasure is buried under East freakin’ Bay Street. That’s the middle of town. It would’ve been discovered decades ago.”

“There’s not much infrastructure underground in that area,” Hi said, “because of the caves. Not even sewer lines.”

“And that’s where the East Bay docks used to be.” Shelton’s voice was suddenly energized. “The ones Bonny used!”

My mind charged ahead, plugging in the pieces. “If our theory’s right, the tunnel entrance should be close to those docks.”

“We need to inspect all the low places,” Hi’s face had reddened with excitement. “Cellars, basements, crypts, anything underground.”

“Can’t we check from the shoreline?” I asked, a bit dubious.

Hi shook his head. “The Battery seawall blocks off the caves. You can’t see anything without scuba gear.”

I snapped my fingers. “I’ve got it.”

Now it was my turn to run home. Twenty steps to the door, straight up the stairs to my bedroom, a bit of pocket rifling, then a dash back down. The roundtrip took less than two minutes.

“Impressive,” Hi said. “But I was carrying hardware.”

“I know how we can get into some downtown basements.” I held out a crumpled flyer. “Anyone up for a ghost tour?”