“They’re what’s known as hardsuits in the trade, right?”

Gunville nodded.

“Remote vehicles are more often used these days. Machines do not share our susceptibility to the hazards of the deep, and there can be no comparison between losing a piece of hardware and losing a human life should some misfortune occur. But our perception, judgment, and manual dexterity remain irreplaceable qualities that robotic craft cannot share. And the hardsuit’s safety record is impressive in calm conditions. I’ve heard of only a single critical incident before the tragedy that took Cédric and his partner, Marius Bouchard.”

“Was Bouchard as good a diver?”

“He lacked the seasoning, but was a trustworthy professional. We send no one down to work at seven hundred meters without comprehensive training and stringent certification.”

“The day those men were lost,” Nimec said. “What went wrong?”

Gunville drank some scotch, lowered his glass to the table.

“A freak calamity,” he said. “They were troubleshooting for the source of a partial system failure and discovered a fault in the cable, a segment that runs along the bottom of an underwater ridge primarily composed of mud and sediment. We believe the damage had been done by sharks. Soon after they tracked it down, there was the apparent submarine equivalent of an earth slide.”

“Anything like that ever happen before? I mean, without your divers getting hurt?”

Gunville shook his head.

“It is what made the incident so shocking. Had it been a massive collapse, I might have perhaps reconciled myself to their deaths . . . gotten my mind around it as you Americans say . . . more easily. When you know someone is in a building that has collapsed, you immediately prepare for the worst. But imagine learning a person has been killed after being struck by a few crumbled bricks or something that has fallen from a construction scaffold. In this case two people. The slide was confined almost to the precise area where Cédric and Marius were working.”

“I wonder what touched it off,” Scull said. He raised his eyes from his soup bowl. “Reports I’ve seen all say the fan’s tectonics are real stable.”

Gunville looked at him.

“That is correct,” he said. “Our best guess is that it was progressive erosion. There are natural interactions that can change the features of the undersea landscape even in salutary conditions. Tidal flows, gravitational effects, storms, scavenging or colonizing creatures. This creates nonconformities. Areas of deterioration that may go undetected, particularly if they are small. Over a long period of time an overhanging portion of the shelf was undermined, fractured, and simply gave.”

Scull grunted. He ran his spoon around the inside of his bowl to clean off the last of the tiébou dienn and put it in his mouth.

“Did you have any seismographs taken afterward?” Nimec said. “Would’ve helped rule out any chance there was a minor quake.”

Gunville shook his head.