Summer swam alongside, then reached down to her dive bag. Uncorking an empty vial, she collected a water sample while they drifted.

“I gathered two additional samples on the way in,” she whispered. “If we can collect another one or two around the dock, then we should have the bases covered.”

“Next stop,” he replied. “Let’s take it underwater from here.”

Dirk took a bearing with a compass on his wrist, then slipped his regulator between his teeth and expelled a burst of air from his BC. Sinking a few feet below the surface, he gently began kicking toward the massive covered dock. The corrugated tin structure was relatively narrow, offering just a few feet of leeway for the ship occupying the lone berth. Yet the dock was well over a football field long, easily accommodating the ninety-meter tanker.

The luminescent dial of the compass was barely visible in the inky water as Dirk followed his set bearing. The water grew lighter from the shoreside lights as he approached the dock entrance. He continued swimming until the dark shape of the tanker’s hull loomed before him. Slowly ascending, he broke the surface almost directly beneath the tanker’s stern rail. He quickly scanned the nearby dock, finding it deserted at the late hour. Pulling his hood away from one ear, he listened for voices, but the drone of the pump house would have made a shout difficult to detect. Gently kicking away from the side of the ship, he tried to get a better look at the vessel.

Though a large ship from Dirk’s perspective, she was tiny as far as LNG carriers go. Designed with a streamlined deck, she could carry twenty-five hundred cubic meters of liquefied natural gas in two horizontal metallic tanks belowdecks. Built for coastal transport duty, she was dwarfed by the large oceangoing carriers that could hold more than fifty times the amount of liquefied natural gas.

The ship was probably ten or twelve years old, Dirk gauged, showing wear at the seams but judiciously maintained. He didn’t know what modifications had been made for the ship to carry liquid CO₂ but presumed they were minor. Though CO₂ was somewhat denser than LNG, it required less temperature and pressure extremes to reach a liquid state. He peered up at the name Chichuyaa, beaded in gold lettering across the stern, noting the home registry of Panama City painted in white lettering below.

A rise of bubbles rippled the water a few yards away, then Summer’s head popped through the surface. She glanced at the ship and dock, then nodded at her brother as she pulled out a vial and collected a water sample. When she finished, Dirk pointed toward the bow and dropped back beneath the surface. Summer followed suit, tracking her brother as he swam forward. Following the dark outline of the tanker’s hull, they swam down the length of the ship, quietly surfacing off the ship’s bow. Dirk eyed the tanker’s Plimsoll line a few feet overhead, noting that the vessel was just a foot or two shy of its fully loaded displacement.

Summer turned her attention to a series of overhead feeder tubes that dangled like thick tentacles over the ship from an adjacent dockside pumping station. Called “Chiksan arms,” the large articulated pipes jimmied and swayed from the surge of the liquid CO₂ flowing through inside. Small wisps of white smoke spewed from the pump building roof, condensation from the cooled and pressurized gas. Summer reached down and retrieved the last empty vial from her dive bag, wondering whether the water around her was contaminated with pollutants as she took the final sample. Zipping the full vial into her dive bag, she kicked toward her brother, who had drifted near the dock.

As she approached, Dirk pointed toward the dock entrance and whispered, “Let’s go.”

Summer nodded and started to turn, then suddenly hesitated in the water. Her eyes fixated on the Chiksan arms above Dirk’s head. With a quizzical look on her face, she raised a finger and pointed at the pipes far overhead. Dirk cocked his head and gazed up at the pipes for a minute but didn’t notice anything amiss.

“What is it?” he whispered.

“There’s something about the movement of the pipes,” she replied, staring at the arms. “I think the carbon dioxide is being pumped onto the ship.”

Dirk stared up at the wiggling arms. There was a rhythmic movement through the pipes, but it was hardly sufficient to tell which way the liquefied gas was flowing. He looked at his sister and nodded. Her occasional hunches or intuitions were usually right. It was enough for him to want to check it out.

“Do you think it means anything?” Summer asked, looking up at the ship’s bow.

“Hard to say if it has any relevance,” Dirk replied quietly. “It doesn’t make any sense that they would be pumping CO₂ onto the ship. Maybe there is an LNG pipeline from Athabasca running through here.”

“Trevor said there was only a small oil pipeline and the CO₂ line.”

“Did you notice if the ship was sitting higher in the water this morning? ”

“I couldn’t say,” Summer replied. “Though she ought to be a lot higher in the water now if she’s been off-loading gas for any amount of time.”

Dirk looked up at the hulking vessel. “What I know about LNG ships, and it ain’t much, is that pumps on shore move the liquid onto the ships, and they have pumps on board to move it off at the destination. From the sound of it, the pump house on shore is clearly operating.”

“That could be to pump the gas underground or into temporary storage tanks.”

“True. But it is too noisy to tell if the shipboard pumps are running.” He kicked a few yards over to the dock, then poked his head up and looked around. The dock and visible portions of the ship were still deserted. Dirk slipped off his tank and weight belt and hung them from a nearby cleat.

“You’re not going aboard?” Summer whispered as if her brother were insane.

Dirk’s white teeth flashed in a grin. “How else will we solve the mystery, my dear Watson?”

Summer knew that waiting in the water for her brother would be too nerve-racking, so she reluctantly hung her dive gear next to his and climbed onto the dock. Following him quietly toward the ship, she couldn’t help muttering, “Thanks, Sherlock,” under her breath.

19

The movement on the monitor was barely discernible. By all rights, the Aleut security guard should have missed it. A fortuitous glance at the bank of video monitors revealed a slight ripple in the water from one of the video feeds, aimed just astern of the tanker. The guard quickly hit a zoom button on the roof-mounted camera, catching sight of a dark object in the water seconds before it disappeared under the surface. Most likely a wayward harbor seal, the guard presumed, but it offered a good excuse to take a break from the dreary confines of the security station.

He reached for a radio and called the watch aboard the Chichuyaa.

“This is plant security. Video picked up an object in the water off your stern. I’m going to take the runabout alongside for a look.”

“Roger, shore,” replied a sleepy voice. “We’ll keep the lights on for you.”

The guard slipped on a jacket and grabbed a flashlight, then stopped in front of a gun cabinet. He eyed a black H&K assault rifle, then thought better of it, tucking a Glock automatic pistol into his holster instead.

“Best not to be shooting seals this time of night,” he muttered to himself as he walked toward the pier.

The LNG carrier emitted a cacophony of mechanical sounds as the chilled gas flowed through the pipes stringing off its deck. Dirk knew there would be a few workers about monitoring the flow, but they were bound to be stationed in the bowels of the ship or at a control panel inside the pump house. Though the dockside area was dimly lit, the ship itself was brightly illuminated and rendered a high degree of exposure. Dirk figured they would need just a minute or two to slip on and determine if the ship’s pumps were operating.