By the time Pitt made his way to the wet lab on the main deck, Giordino was scrolling through the AUV’s sonar images on a large-panel display. Pitt noticed the seafloor was much more dramatic than the earlier sites, with rocky outcroppings and undulating hills and valleys.
He took a seat next to Giordino. “Your AUV got a workout on this run.”
“That’s what she’s made for.” Giordino pointed to an insert on the screen that portrayed the overall search grid and their relative location. “If the drift estimates are correct, there’s a high probability the source of the mercury release is within the quadrant just surveyed.”
“Let’s hope there’s a visible indicator this time,” Pitt said.
They reviewed nearly an hour of sonar images. While the seafloor did flatten, no man-made objects were apparent. Finally, Pitt noticed a shadow on the seabed and had Giordino halt the scrolling.
“Zoom in on that streak,” he said. “It looks like a linear path across the bottom.”
Giordino nodded and enlarged the image. “There’s an even pair of lines. They look too precise to be geography.”
“Let’s see where it goes,” Pitt said.
Giordino resumed scanning. The faint lines appeared in greater concentration in a section of the grid that dipped into a large depression. Pitt was tracking the change in depth when Giordino froze the image.
“Well, lookie here,” he said. “Somebody lost a boat.”
A dark, slender object rose from the bottom, casting a short shadow. Familiar linear tracks edged nearby.
“It looks long and lean,” Pitt said. “Perhaps a sailing boat that’s partially buried.”
“The AUV was running at a low frequency to scan a wider path, so the definition is on the weak side. That blur of a boat looks to be about thirty feet long.”
“Doubtful it’s our mercury source but maybe worth a look.”
Giordino resumed scrolling until the AUV’s records came to an end. Pitt noted the vehicle’s last recorded depth before it returned to the surface.
“I’m afraid that’s all she wrote,” Giordino said. “Some shadowy lines and a small boat.”
Pitt poked a finger at the now blank screen. “The AUV’s depth recorder indicated something of a depression in the middle of that grid. It may be nothing, but if that area is the source of the mercury contamination, it might be worth examining from a broader spectrum. Can a mosaic image of the entire survey grid be assembled? Or at least major blocks of it?”
“Piece of cake. All it will take is a little seat time at the keyboard.”
“Fine, but you better pass it off to someone else. You’ve got a more immediate job.”
“What’s that?”
“Firing up the ship’s submersible,” Pitt said. “I want to see for myself what’s happening down there.”
24
My friends, I am glad to see that you are well.”
Dr. Madero’s relief at seeing Dirk and Summer barely registered in his voice. His face formed a gaunt mask of shock and angst as he ushered them into the lab beside his university office.
“We feel terrible about Dr. Torres,” Summer said. “If I hadn’t found the codex . . .”
“No, no, it is a remarkable find. Besides, I can say with certainty that Miguel died doing what he loved best.” His voice turned nearly to a whisper. “I’m only sorry that the police have been unable to apprehend the killers.”
“They fished one of them out of the river below the hydroelectric plant,” Dirk said. “Unfortunately, he was so pulverized, there wasn’t much left to identify. Do you have any idea who would have killed Dr. Torres for the stone?”
Madero shook his head and grimaced. “It could be forces from anywhere, maybe even outside the country. We’ve had lots of problems around Tula with the black market trade of Toltec relics. The thieves probably don’t even know what they have.”
“I got the distinct impression,” Summer said, “they knew exactly what they were after.”
“I will remain hopeful that the stone will be recovered,” Madero said in a weak voice, “and Miguel’s death avenged.”