"George Washington picked the spot himself," Mike said. "Considered it one of the most critical positions on the American continent."

"Why?" I asked.

The Hudson took a sharp S-shaped curve just above the hilltop setting of the original fortifications.

" 'Cause you could control all the river traffic from this place. South to New York, north to New England, and west to the Great Lakes. The Brits would have split the colonies in half-right down there-if Benedict Arnold had succeeded in giving the Point away, like he tried."

"Here's your rock," Galiano said. "Pollepel Island."

On the right side of the river, not far above West Point, the turrets of an enormous castle rose above the dense green growth that covered the ground.

Galiano swooped his bird close in on the south side and started to circle to the west of the abandoned ruin.

Mike gripped the seat back even tighter. He looked out the window, and I knew he was trying to see where Galiano would put down the chopper. "Hey, Sarge," he said, "I didn't bring the rosary beads."

"I'd say it's a little bit like Walt Disney meets Stephen King. Give me a minute."

As we hovered at the north end of the island I noted four or five more buildings, mostly roofless, smaller than the six-story castle that soared above the gray waters of the Hudson.

"There," Mercer said, pointing down through the glass bubble of the helicopter's nose. "Check it out. State police and army craft, off to the east."

On the edge of the rocky shore, there was a small cluster of boats.

Like the NYPD's emergency rescue craft, they had large initials on their tops and sides, for identification by other agencies approaching by air or sea.

Several men in windbreakers marked with orange neon sleeve reflectors were waving their arms at Galiano.

"Got it," he said. "There's a clearing on the southeast. That'll do me fine."

Mike closed his eyes and pulled his seat belt tighter. The chopper continued around the far side of the structures, banking as it made the final approach. It hovered again, swaying from side to side as Galiano took great care to avoid the surrounding trees and center on the only flat strip of land we had seen.

The big machine hit the ground with a thud, and we waited for the powerful rotors to come to a stop.

I could see the tops of the ruined castle and the thick tangle of weeds and vines that had swallowed the buildings' foundations. "It looks like we've traveled back in time," I said. "To another century."

"To a ghost island, Coop. That's what this place is," Mike said.

"Maybe we got some new ghosts now.

A tall, heavyset man a little older than I held out a hand to guide me down from the chopper. "Step lively, miss. Snakes, spiders, ticks, and poison sumac."

"We were with his cousin, poison ivy, yesterday. I'm Mike Chapman." He introduced Mercer and me to our official greeter

Bart Hinson. State police. The brush that surrounded our landing pad was as tall as the trees behind it. Boulders and branches ringed the clearing that had been hacked out this morning for our arrival

Any developments?" Mike asked

Just trying to make sense of what we have here. Nothing much got done overnight. It's not easy terrain to search. Follow me," Bart said.

We entered a trail about twenty feet long, ducking beneath weathered limbs that had been intertwining, it appeared from their density, for many years. When we emerged, I faced the most unusual array of huge stone buildings-all with turrets and towers, elaborate carvings, and coats of arms.

The men waiting for us next to a crumbling entrance to the building complex were from a mix of agencies. There were six other troopers-two of whom specialized in crime scene work-four landscapers who'd been called in with chainsaws to make room for us to land, and a caretaker who lived on the mainland but supervised the property for the state.

Bart Hinson was the lead man. "I thought we'd show you where the girl's body was discovered," he said. "Tell you a little bit about this place."

I craned my neck to look up the side of one of the buildings that was about a city block long. It was covered in red paint that had faded over time. Written across it in chipped and mottled gold lettering were the words BANNERMAN ISLAND ARSENAL

You find the boat yet?" Mike asked. "That must be how the killer got her here."

Bart shook his head. "Well, up this way, everybody and his uncle has a boat. More docks than you got subway platforms. Fancy namebrand little yachts, simple outboard motors, fishing boats-just about every size and shape. Then you got your kayaks and canoes."

"I hear you."

Bart pointed at the caretaker. "He uses an aluminum rowboat to go back and forth. Wouldn't take much to slip over here and back even with someone else's boat and nobody ever know."

"How about the currents?" Mercer asked.

"This part of the Hudson is an estuary, so the tide changes from north to south a couple of times a day," Bart said. "It's been pretty calm this week. A strong rower wouldn't have much trouble if he knew the tides."

"I thought this was called Pollepel Island," I said, pointing up at the writing on the wall. "What's that sign about?"

"Pollepel was its name centuries ago. The Native Americans spun tales that this spot was haunted. Then along came the Dutch sailors, who had good cause to believe it was spooked, too," Bart said. "Thought it was the devil made the ships crash into the rocks and sink with all their goods aboard."

"Was this fortress part of West Point? Did the army build it to defend the Hudson from the east?"

Mike dismissed me. "It has nothing to do with the government."

"But you said the state owns it."

"That's only been the last thirty years," Bart said. He swept his arm around the bizarre vista. "This was all the folly of one man, Alex. A privately owned island, bought in 1900 by a complete eccentric named Frank Bannerman."

"And he built this-this…?"

"It's supposed to look like an ancestral family castle back in Scotland, complete with drawbridges and a moat. But you're right to call it a fortress. The arsenal-that's the second-largest building here-was one of the biggest munitions warehouses in America. Nations went to war a century ago outfitted entirely by Frank Bannerman, from his crazy island outpost."

"You know about this guy, Mike?" Mercer asked.

"My aunt Eunice had a cellar full of Bannerman's catalogs. Probably still does. Uncle Brendan had been collecting them since he was a kid."

Mike's military interests had been fueled by his father's oldest brother, who had landed at Normandy.

"What was Bannerman doing up here?" Mercer asked.

"The family emigrated from Scotland to New York in the 1850s, right after he was born," said Bart. "At the end of the Civil War, young Frank started buying up tons of military goods-surplus equipment- that the government was auctioning off. He purchased everything from scrap metal and bayonets to ships that the navy wanted to unload, figuring he could sell them to whatever government went to war next."

"He had all the weapons and ammunition stored in offices downtown, on Broadway," Mike said.

"Till after the Spanish-American War. Bannerman purchased 90 percent of all the military hardware and black powder when that conflict ended, but it was so dangerously explosive that the city demanded he move it out. In 1900, he bought this island and moved everything up our way," Bart said. "Designed all the buildings himself."

"Did he live here?" I asked.

"That castle," Bart said, pointing at the enormous structure with four rounded towers and crenellated peaks, "was built to be a house for his family. See how there's not a right angle anywhere on it? The guy was a master of detail."