“THEY SIMPLY DOVE in and vanished.”

Pitt crouched on one knee and stared past the half-submerged tractor into the black ominous water. He was tired from jet lag, and he’d barely slept a couple of hours on the plane from Washington. How rotten not to have time to enjoy a good breakfast at a local inn and sleep past noon, he wallowed in self-pity.

“Their safety lines were sliced apart.” The young officer who led the German naval dive team held up a nylon line whose end appeared razor-severed. “By what? We can’t begin to guess.”

“Communication line too?” Pitt slowly sipped at a cup of coffee. He picked up a small stone with his free hand and idly tossed it in the water, observing the ripples that spread from the splash.

“The phone line connected to the lead diver was also cut,” admitted the German. He stood tall and well muscled. His English carried only a slight trace of an accent. “Soon after the two man team dropped into the pond, they discovered an underwater tunnel leading to the west. They swam a distance of ninety meters before reporting the tunnel ended at a small chamber with a steel door. A few minutes later the phone and safety lines went slack. I sent another team in to investigate. They disappeared like the others.”

Pitt turned his head and looked at the men of the German Navy dive team who stood helpless and saddened at the loss of their friends. They were clustered around the folding tables and chairs of a portable command post manned by a group of police underwater rescue divers. A trio of men in civilian clothes, who Pitt assumed were government officials, questioned the divers in low voices.

“When did the last man go in?” Pitt asked.

“Four hours before you arrived,” said the young dive officer, who had introduced himself as Lieutenant Helmut Reinhardt. “I had a devil of a time keeping the rest of my men from following. But I’m not about to risk another life until I know what’s going on in there.” He paused and tipped his head toward the police divers, who were attired in bright orange dry suits. “Those idiot police, however, think they’re invincible. They’re planning to send one of their teams inside.”

“Some people are born for suicide,” said Giordino with a yawn. “Take me for example. I wouldn’t go in there without a nuclear submarine. No daredevil ventures by Mrs. Giordino’s boy. I intend to die in bed entwined with an erotic beauty from the Far East.”

“Don’t pay any attention to him, ” said Pitt. “Put him in a dark place and he hallucinates.”

“I see,” murmured Reinhardt, but obviously he didn’t.

Finally Pitt rose and nodded in Frank Mancuso’s direction. “Booby-trapped,” he said simply.

Mancuso nodded. “I agree. The entrances to the treasure tunnels in the Philippines were packed with bombs rigged to go off if struck by digging equipment. The difference is the Japs planned to return and retrieve the treasure, while the Nazis intended for their booby traps to destroy the loot along with the searchers.”

“Whatever trapped my men in there,” said Reinhardt bitterly, unable to say the word “killed,” “was not bombs.”

One of the official-looking men walked over from the command post and addressed Pitt. “Who are you, and whom do you represent?” he demanded in German.

Pitt turned to Reinhardt, who translated the question. Then he refaced his interrogator. “Tell him the three of us were invited.”

“You are American?” the stranger blurted in broken English, his face blank in astonishment. “Who gave you authorization to be here?”

“Who’s this mook?” Giordino inquired in blissful ignorance.

Reinhardt couldn’t suppress a slight grin. “Herr Gert Haider, Minister of Historic Works. Sir, Herr Dirk Pitt and his staff from the American National Underwater and Marine Agency in Washington. They are here at the personal invitation of Chancellor Lange.”

Haider looked as if he’d been punched in the stomach. He quickly recovered, straightened to his full height, half a head short of tall, and attempted to intimidate Pitt with a superior Teutonic demeanor. “Your purpose?”

“We’ve come for the same reason as you,” replied Pitt, studying his fingernails. “If old interrogation records of Nazi officials in your Berlin archives and our Library of Congress are correct, eighteen thousand works of art were hidden in excavated tunnels under a secret airfield. This could very well prove to be that secret airfield with its art depository chamber extending somewhere beyond the water barrier.”

Haider wisely realized he couldn’t bluster the tough, purposeful-looking men dressed in loose blue-green Viking dry suits. “You know, of course, any art that is found belongs to the German Republic until it can be traced and returned to the original owners.”

“We’re fully aware of that,” said Pitt. “We’re only interested in one particular piece.”

“Which one?”

“Sorry, I’m not allowed to say.”

Haider played his last card. “I must insist the police dive team be the first to enter the chamber.”

“Fine by us.” Giordino bowed and gestured toward the dark water. “Maybe if one of your deputies is lucky enough to make it in and back, we’ll find out what’s eating people in that hell hole down there.”

“I’ve lost four of my men.” Reinhardt spoke solemnly. “They may be dead. You cannot allow more men to die through ignorance of the unknown.”

“They are professional divers,” Haider retorted.

“So are the men I sent in there. The finest divers in the Navy, in superior condition and more extensively trained than the police rescue team.”

“May I suggest a compromise,” said Pitt.

Haider nodded. “I’m willing to listen.”

“We put together a seven-man probe team. The three of us because Mancuso here is a mining engineer, an expert on tunnel construction and excavation, while Al and I are experienced in underwater salvage. Two of Lieutenant Reinhardt’s Navy men, since they’re trained in defusing any demolitions we might encounter. And two of the police divers as rescue and medical backup.”

Haider stared into Pitt’s eyes and saw only grim tenacity. It was a solid proposal fortified with logic. He forced a smile. “Who goes in first?”

“I do,” Pitt said without hesitation.

His two short words seemed to echo in the cavern for long seconds, and then the tension suddenly evaporated and Haider stuck out his hand.

“As you wish.” He shook Pitt’s hand and puffed out his chest to regain an image of authoritative dignity. “But I hold you responsible, Herr Pitt, if you trip any explosive devices and destroy the artworks.”

Pitt gave Haider a contemptuous grin. “In that case, Herr Haider, you may have my head—literally.”

Pitt set the time on the microelectronic computer attached by a line to his air tank and made a final check of his regulator and buoyancy compensator. For the fiftieth time since dropping down the ladder from farmer Clausen’s field he stared into the beckoning black pool.

“Your gears are turning,” observed Giordino as he adjusted the straps to his tank pack.

Pitt rubbed his chin thoughtfully without replying.

“What do you think is going on in there?” asked Mancuso.

“I think I’ve solved half the puzzle,” answered Pitt. “But the cutting of the lines? Now that’s downright puzzling.”

“How’s your acoustic speaker?” asked Mancuso.

Pitt inserted the regulator’s mouthpiece and spoke into it. “Mary had a little lamb…” The words came out muffled but understandable.

“I guess it’s time, fearless leader,” grunted Giordino.

Pitt nodded at Reinhardt, who was accompanied by one of his men. “Ready, gentlemen? Please try to stay within two meters of the man in front of you. Visibility appears to be four meters, so you should have no trouble keeping the distance. My team will communicate with you through our acoustic speakers.”