"See anything that resembles an air vent to a tunnel?"

"It must come up through the central battlement."

Giordino was glad there was no moon. "So how do we get over the fence, past the security cameras, security alarms, security guards and the dogs?"

"First things first. We can't deal with the security until we penetrate the fence," Pitt replied, quietly absorbed in studying the fortress grounds.

"And how do we do that? It must be ten feet high."

"We could try pole-vaulting over it."

Giordino looked at Pitt queerly. "You must be kidding."

"I am." Pitt pulled a coil of rope from his knapsack. "Can you still climb a tree or does your arthritis limit any physical activity?"

"My aging joints aren't half as stiff as yours."

Pitt slapped his old friend on the shoulder. "Then let's see if two old fogeys can still perform daring feats of agility."

After breakfast at the lodge, and true to their word with Rathbone, Pitt and Giordino had latched on to a tour guide who was leading a dozen tourists through the wildlife reserve, and took a nature hike. They hung in the back of the group, talking between themselves as the tour progressed, hardly noticing the abundance of wildly colored birds and strange animals.

When they returned to the lodge, Pitt made some discreet inquiries about the old man and, as he suspected, the employees of the lodge said that as far as they knew, Rathbone was simply a guest who had showed a Panamanian passport when he registered. If he owned a chain of lodges up and down the river, it was news to them.

At noon, they loaded up the Greek Angel with their gear and a few sandwiches from the kitchen and shoved off into the river. The engine caught on the first flick of the starter and they headed out of the lagoon into the main current of the San Juan. The virgin jungle gave way to more open land enhanced by green rolling hills, with trees neatly spaced as if planted by a landscaper in a vast park.

El Castillo was only six kilometers upriver and they had crawled along at a pace just slightly above idle, rounding the final bend an hour later before passing under the colonial fortress that loomed above the town. Moss spread over the ancient lava rock ruins, giving it the appearance of an ugly blot on an otherwise gorgeous landscape, while the picturesque little town below, with its roofs of red tin and colorfully painted pangas littering the riverbank, seemed an inviting oasis.

Except for river traffic, the village of El Castillo was completely detached from the rest of the world. There were no roads in or out, no cars and no airport. The residents subsisted by farming the encircling hills, fishing and working in the sawmill or palm oil factory twenty kilometers up the river.

Pitt and Giordino wanted to be seen coming and departing from the little fishing community as they continued their cruise up the river toward Lake Nicaragua, so they tied up the panga at a small dock and walked about fifty yards up a dirt road toward a little hotel with a bar and restaurant. They passed several gaily painted wooden houses and waved to three freshly scrubbed little girls in yellow dresses who were playing barefoot on a porch.

They saved their sandwiches from the kitchen of the Refugio Bartola for the coming night excursion and ordered a lunch of fresh fish from the river, downed by the local beer.

The owner, whose name was Aragon, waited on their table. "May I recommend the gaspar. It's not often caught, and when prepared with my special sauce, it is a great delicacy."

"Gaspar," repeated Giordino. "Never heard of that one."

"A living relic millions of years old with armored scales, a snout and fangs. I promise you'll never be able to enjoy it anyplace but here."

"I'm always game for an adventure in gourmet dining," said Pitt. "Bring on the gaspar."

"I'm only going along with great trepidation," Giordino muttered.

"Too bad about the fortress being off-limits," said Pitt conversationally. "I hear the museum was worth a visit."

Aragon stiffened slightly and looked furtively through a window at El Castillo. "Si, senor, it is a pity you must miss it. But the government closed it down as too dangerous for tourists."

"Looks pretty sturdy to me," said Giordino.

Aragon shrugged. "All I know is what the police from Managua told me."

"Do its guards stay in town?" asked Pitt.

Aragon shook his head. "They set up a barracks inside the fortress and are rarely seen except when they are relieved by helicopter from Managua."

"None leave the fort, even for food, drink or pleasure?"

"No, senor. They do not socialize with us. Nor do they allow anyone within ten meters of the fence."

Giordino poured his bottle of beer into a glass. "First time I ever heard of a government keeping tourists out of a museum because it might fall down."

"Do you gentlemen wish to stay at the hotel tonight?" asked Aragon.

"No, thank you," answered Pitt. "I'm told there are rapids upriver and we'd like to pass through while it's still light."

"You shouldn't have a problem if you stay inside the channel. Boats rarely overturn in the rapids if people are careful. It's the crocodiles in calm water that present a problem to anyone who falls over the side."

"Does your restaurant serve steak?" Pitt inquired.

"Si, senor. Do you wish more to eat?"

"No, we'd like to take the meat with us for later. Once we pass through the rapids, my friend and I will camp onshore and cook dinner over a fire."

Aragon nodded. "Be sure and camp inland from the banks of the river or you might become food for a hungry crocodile."

"Feeding a croc wasn't exactly what I had in mind," Pitt said, with a broad smile.

Departing late in the afternoon, they cruised through the rapids above El Castillo without mishap until they were out of sight of the town. Seeing no other pangas but their own between bends in the river, they drove the Greek Angel onto the bank, raised the outboard motor and pulled it into the lush underbrush until it was completely hidden from all water traffic.

While it was still light, they found a narrow path that headed toward the town. Then they ate their sandwiches and relaxed and slept till after midnight. Moving cautiously along the path while using their nightscope to penetrate the night, they skirted the little houses and made their way into a thicket of bushes, where they lay now and studied the security surrounding the fortress, spotting and marking the TV security cameras in their minds.

A light drizzle began to fall and soon their thin clothes were soaked through. Standing in a rain in the tropics was like standing in a shower at home. The water temperature was as comfortable to the skin as if it had been preset on a faucet.

When ready, Pitt, followed by Giordino, climbed into a high jatoba tree that towered more than a hundred feet high with a trunk diameter of four feet. The tree stood within several feet of the fence around the fortress, and its lower limbs stretched far over the fence top that was circled with a razor-sharp spiral of steel. Throwing a looped rope around a thick branch ten feet above, Giordino climbed up onto a higher limb before crawling through the smaller branches until he was beyond the fence and twelve feet above the ground. There he paused and swept the ground below with the nightscope.

Using the rope, Pitt hauled his body upward with his hands while his feet walked the tree trunk. Reaching the limb, he crept through the branches until he was even with Giordino's booted feet. "Any sign of the guards and their dogs?" he whispered.