The mystery of who put the oil in Egan's leather case was set aside as Pitt and Giordino began checking and testing the I equipment and electronic systems of the Sea Sleuth, the survey vessel's autonomous underwater vehicle (AUV). During the voyage to the grave of the Emerald Dolphin, they discussed the wreck probe procedure with Captain Burch and the ocean engineers on board. All agreed that for reasons of safety the autonomous vehicle should be sent down first rather than the manned submersible, Abyss Navigator. There was nothing sleek or streamlined about the design of the Sea Sleuth. She was the extreme of functional design. Utilitarian and expedient, she made a Mars lander look artistic. Seven feet high by six feet wide by seven feet in length, she weighed in at slightly less than seven thousand pounds. Her skin was a thick layer of titanium, and from a distance she looked like a huge elongated egg open on the sides, standing on sled runners. A circular protrusion on top housed her two variable-buoyancy tanks. Support tubes laced her inner construction beneath the variable-buoyancy tanks.

Mounted inside, almost as if they had been placed there by a child with his Lego set, were high-resolution video and still cameras, a computer housing and sensors that recorded salinity, water temperature and oxygen content. A pressure-balanced, direct-drive DC motor provided her propulsion and was energized by a powerful manganese-alkaline battery system. Highly sophisticated transducers transported signals and imagery through the watery depths to the mother ship far above on the surface, and it sent control signals in return. Her path was illuminated by an array of ten external lights.

Like some mechanical monster out of a science-fiction movie, a complicated robotic arm, or manipulator, as it was called, extended from one side of the vehicle. It had the muscle to lift a four-hundred-pound anchor and the sensitivity to pick up a teacup.

Unlike earlier robotic vehicles, Sea Sleuth was untethered and had no umbilical cord connected to controls in the pilothouse. She was completely autonomous; her propulsion and video cameras were operated from the command room of the Deep Encounter thousands of feet above.

A crewman came up to Pitt as he was helping Giordino adjust the robotic arm. "Captain Burch said to let you know that we're three miles from the target."

"Thank you," said Pitt. "Please tell the skipper that Al and I will join him shortly."

Giordino threw a pair of screwdrivers into a toolbox, stood up and stretched his back. "She's ready as she'll ever be."

"Let's head up to the bridge and see how the Dolphin looks on the side scan sonar."

Burch and several other NUMA engineers and scientists were in the command center compartment just aft of the pilothouse. Everyone's faces and hands were reflected in a weird purplish cast from the overhead lighting. Recent experiments had determined that instrumentation was easier to read for long elements of time under a red-blue wave band of light.