“It would be astounding,” Suzanne responded. “They occur up and down the Mid-Atlantic Ridge system, but finding one at such a distance from the ridge, and through the middle of what we assume is an old volcano, would be quite unique.”

“Let’s go take a look,” Perry suggested. “This place is fascinating.”

Suzanne grinned in triumph. She glanced at Donald. Even he couldn’t suppress a smile. He’d been sympathetic to Suzanne’s plan but had not been optimistic.

It took Suzanne only a few minutes to unload everything that Mark had stowed in the submersible’s tray. Once the material was lined up next to the well head, she folded the manipulating arms into their retracted position.

“So much for that job,” Suzanne said. She turned off the power to the servo links.

“ Oceanus to surface control,” Donald said into the UQC mike. “The payload has been off-loaded. What’s the status of the divers?”

“Compression is nearing depth,” Larry’s voice reported over the speaker. “The bell should be starting its descent shortly. ETA on the bottom, thirty minutes give or take five.”

“Roger!” Donald said. “Keep us informed. We are going to move due west to investigate a scarp we caught sight of on the last dive.”

“Ten-four,” Larry said. “We’ll let you know when the bell is lifted off the DDC. We’ll also let you know when it is passing through five hundred feet so you can take up an appropriate position.”

“Roger!” Donald repeated. He hung up the UQC mike. With his hands resting gently on the joysticks he jacked up the power to the propulsion system to fifty amps. He expertly guided the submersible away from the well head, careful to avoid the vertical run of pipe. A few moments later the Oceanus was slowly flying over the strange topography of the guyot’s top.

“What I believe we’re looking at here is a pristine section of the mantle’s crust,” Suzanne said. “But how and why the lava cooled to form these polygonal shapes is beyond me. It’s almost like they’re gigantic crystals.”

“I like the idea of it being Atlantis,” Perry said. His face remained glued to the view port.

“We’re coming up to the place where we glimpsed that fault,” Donald said.

“It should be just over that ridge of columns coming up,” Suzanne said for Perry’s benefit.

Donald cut back on the power. The submersible slowed as they cleared the ridge.

“Wow!” Perry commented. “It certainly drops off quickly.”

“Well, it’s not a transverse fault,” Suzanne said as she got a full view of the formation. “In fact, if it were a fault at all it would have to be a graben. The other side is just as steep.”

“What the hell is a graben?” Perry asked.

“It’s when a fault block falls in relation to the rock on either side,” Suzanne explained. “But something like that doesn’t happen on the top of a seamount.”

“It looks like a huge rectangular hole to me,” Perry said. “What would you say? About a hundred and fifty feet long and fifty wide?”

“I’d say that’s about right,” Suzanne said.

“It’s incredible!” Perry commented. “It’s like some giant took a knife and cut out a chunk of rock just the way you’d take a plug out of a watermelon.”

Donald powered the Oceanus out over the hole, and they all looked down.

“I can’t see the bottom,” Perry said.

“Neither can I,” Suzanne said.

“Neither can our sonar,” Donald said. He pointed to the echo sounder monitor. It wasn’t getting a return signal. It was as if the Oceanus were poised over a bottomless pit.

“My word!” Suzanne said. She was dumbfounded.

Donald gave the monitor a tap, but there was still no readout.

“That’s very strange,” Suzanne said. “Do you think it’s malfunctioning?”

“I can’t tell,” Donald reported. He tried changing the adjustments.

“Wait a sec,” Perry voiced tensely. “Are you two pulling my leg?”

“Try the side-scan sonar,” Suzanne suggested, ignoring Perry for the moment.

“It’s just as weird,” Donald said. “The signal is aberrant unless we want to accept the pit’s only six or seven feet deep. That’s what the side-scan monitor is suggesting.”

“Clearly the hole is a lot deeper than six or seven feet,” Suzanne said.

“Obviously,” Donald agreed.

“Hey, come on, you guys,” Perry said. “You’re starting to scare me.”

Suzanne turned briefly to face Perry. “We’re not trying to scare you,” she said. “We’re just mystified by our instruments.”

“My guess is there’s one hell of a thermocline just within the rim of this formation,” Donald said. “The sonar has to be bouncing off something.”

“Would you mind translating that?” Perry said.

“Sound waves bounce off sharp temperature gradients,” Suzanne said. “We think that’s what we have here.”

“In order to get a depth readout we have to descend ten or fifteen feet into the pit,” Donald said. “I’ll do that by decreasing our buoyancy, but first I want to change our orientation.”

With short bursts Donald used the starboard front thruster to turn the submersible until it became parallel with the long axis of the hole. Then he manipulated the variable ballast system to make the sub negatively buoyant. Gradually the submersible started down.

“Maybe this isn’t such a good idea,” Perry said. He was nervously looking back and forth between the side-scan sonar monitor and his view port.

The UQC speaker cracked to life: “Surface control to Oceanus. The bell is lifting off the DDC as I’m speaking. The divers will be passing through five hundred feet in about ten minutes.”

“Roger, surface control,” Donald said into the mike. “We’re about one hundred feet west of the well head. We’re going to check out an apparent marked thermocline in a rock formation. Communications might be interrupted momentarily, but we’ll be on station for the divers.”

“Ten-four,” Larry’s voice said.

“Look at the luster of the walls,” Suzanne remarked as the submersible sank below the tip of the huge hole. “They’re perfectly smooth. It almost looks like obsidian!”

“Let’s head back to the well head,” Perry suggested.

“Could this be an opening into an extinct volcano?” Donald asked. A slight smile flitted across his otherwise rigid face.

“That’s a thought,” Suzanne said with a laugh. “Although I have to say I’ve never heard of a perfectly rectilinear caldera.” She laughed again. “Our dropping down in here like this reminds me of Jules Verne’s Journey to the Center of the Earth.”

“How so?” Donald asked.

“Have you read it?”

“I don’t read novels,” Donald said.

“That’s right, I forgot,” Suzanne said. “Anyway, in the story the protagonists entered a kind of pristine netherworld via an extinct volcano.”

Donald shook his head. His eyes stayed glued to the thermistor readout. “What a waste of time reading such rubbish,” he said. “That’s why I don’t read novels. Not with all the technical journals I can’t get to.”

Suzanne started to respond but changed her mind. She’d never been able to make a dent in Donald’s rigid opinions about fiction in particular and art in general.

“I don’t mean to be a pest,” Perry said, “but I-”

Perry never got out the last part of his sentence. All at once the submersible’s descent accelerated markedly and Donald cried out, “Christ almighty!”

Perry gripped the sides of his seat with white-knuckle intensity. The rapid increase in downward motion scared him, but not as much as Donald’s uncharacteristic outburst. If the imperturbable Donald Fuller was upset, the situation must be critical.

“Jettisoning weights!” Donald called out. The descent immediately slowed, then stopped. Donald released more weight and the sub began to rise. Then he used the port-side thruster to maintain orientation with the long axis of the pit. The last thing he wanted was to hit up against the walls.

“What the hell happened?” Perry demanded when he could find his voice.