His concentration never flickered while Pitt, feet extended as bumpers, came to an abrupt stop against the console beside him.

Pitt watched the computer-enhanced sonograph as the ridge of a crater slowly rose to a crest and then made a steep descent into the interior void.

"She's dropping fast," said Giordino.

Pitt glanced at the echo sounder. "Down from 140 to 180 meters. "

"Hardly any slope to the outer rim."

"Two hundred and still falling."

"Weird formation for a volcano," said Giordino. "No sign of lava rock."

A tall, florid-faced man with thick graying brown hair that struggled to escape from a baseball cap tilted toward the back of his head, opened the door and leaned in the compartment.

"You night owls in the mood for food or drink?"

"Peanut-butter sandwich and a cup of black coffee sounds good," Pitt replied without turning. "Leveling out at 220 meters. "

"A couple of doughnuts with milk," Giordino answered.

Navy Commander Byron Knight, skipper of the survey vessel, nodded.

Besides Pitt and Giordino, he was the only man with access to the electronics compartment. It was off limits to the rest of the officers and crew.

"I'll have your orders rustled up from the galley."

"You're a wonderful human being, Byron," Pitt said with a sarcastic smile. "I don't care what the rest of the navy says about you."

"You ever try Peanut butter with arsenic?" Knight threw at him over his shoulder.

Giordino watched intently as the arc of the formation spread and widened. "Diameter almost two kilometers."

"Interior is smooth sediment," said Pitt. "No breakup of the floor."

"Must have been one gigantic volcano."

"Not a volcano."

Giordino faced Pitt, a curious look in his eyes. "You have another name for a submerged pockmark?"

"How about meteor impact?"

Giordino looked skeptical. "A meteor crater this deep on the sea bottom?"

"Probably struck thousands, maybe millions of years ago, at a time when the sea level was lower."

"What led you up that street?"

"Three clues," Pitt explained. "First, we have a well defined rim without a prominent outer upsiope. Second, the subbottom profiler indicates a bowl-shaped cross section. And third" he paused, pointing at a stylus that was making furious sweeps across a roll of graph paper.

"The magnetometer is having a spasm. There's enough iron down there to build a fleet of battleships."

Suddenly Giordino stiffened. "We have a target!"

"Where?"

"Two hundred meters to starboard, lying perpendicular on the crater's slope. Pretty vague reading. The object is partly obscured by the geology."

Pitt snatched the phone and rang the bridge. "We've had a malfunction in the equipment. Continue our heading to the end of the run. If we can make the repair in time, come around and repeat the track."

"Will do, sir," replied the watch officer.

"You should have sold snake oil," said Giordino, smiling.

"No telling the size of Soviet ears."

"Anything from the video cameras?"

Pitt glanced at the monitors. "Just out of range. They should pick it up on the next pass."

The initial sonar image that appeared on the recording paper looked like a brown smudge against the lighter geology of the crater's wall. Then it slipped past the sidescan's viewing window and disappeared into a computer that enhanced the detail. The finished picture came out on a special large high-resolution color video monitor. The smudge had become a well defined shape.

Using a joystick, Pitt moved a pair of crosshairs to the center of the image and clicked the button to expand the image.

The computer churned away for a few seconds, and then a new, larger, even more detailed image appeared on the screen. A rectangle automatically appeared around the target and showed the dimensions. At the same time another machine reproduced the color image on a sheet of glossy paper.

commander Knight came rushing back into the compartment. After days of tedium, cruising back and forth as though mowing a vast lawn, staring for hours on end at the video display and sidescan readings, he was galvanized, anticipation written in every line of his face.

"I was given your message about a malfunction. You have a target?"

Neither Pitt nor Giordino answered. They smiled like prospectors who have hit the mother lode. Knight, staring at them, suddenly knew.

"Good God above!" he blurted. "We've found her, really found her?"

"Hiding in the seascape," said Pitt, pointing to the monitor while handing Knight the photo. "The perfect image of one Alfa-class Soviet submarine."

Knight stared, fascinated, at both sonar images. "The Russians probed all around this section of the sea. Incredible they didn't find her."

"She's easy to miss," said Pitt. "The ice pack was heavier when they conducted their search. They couldn't maintain a straight track.

Probably skirted the opposite side of the upslope, and their sonar beams only showed a shadow where the sub was lying. Also, the unusually heavy concentration of iron under the crater would have thrown off their magnetic profile."

"Our intelligence people will dance on the ceiling when they see this."

"Not if the Reds get wise," said Giordino. "They'll hardly stand idle and watch us repeat our 'Seventy-five snatch of their 'Golf' class sub with the Glomar Explorer."

"You suggesting they haven't swallowed our story about conducting a geological survey of the seafloor?" Pitt asked with deep sarcasm.

Giordino gave Pitt a sour look indeed. "Intelligence is a weird business," he said. "The crew on the other side of these bulkheads has no idea of what we're up to, yet Soviet agents in Washington smelled out our mission weeks ago. The only reason they haven't interfered is because our undersea technology is better and they want us to lead the way to their sub."

"Won't be easy to deceive them," agreed Knight. "Two of their trawlers have been shadowing our every move since we left port."

"So have their surveillance satellites," added Giordino.

Pitt said, "All reasons why I asked the bridge to run out our last track before coming about for a closer look."

"Good try, but the Russians will pick up our track rerun."

"No doubt, except once we pass over the sub we go on and Turn onto the next lane, continuing as before. Then I'll radio our engineers in Washington to complain of equipment problems and ask for maintenance instructions. Every couple of miles we'll rerun a lane to reinforce the ruse."

Giordino looked at Knight. "They might buy it. It's believable enough."

Knight considered that. "Okay, we won't hang around. This will be our last look at the target. Then we continue on, acting as if we've found nothing."

"And after we've finished this grid," Pitt said, "we can start a new one thirty miles away and fake a discovery."

"A nice added touch," Giordino said approvingly. "Drop a red herring across our trail."

Knight smiled wryly. "Sounds like a good script. Let's go for it."

The ship rolled and the deck canted slightly to starboard as the helmsman brought her around on a reverse course. Far behind the stern, like an obstinate dog on a long leash, a robot submersible called Sherlock automatically refocused its two movie cameras and one still camera while continuing to send out probing sonar waves. Presumedly named by its designer after the fictional detective, Sherlock revealed detailed features of the seafloor previously unseen by man.