While they were preparing for their excursion, Linda engaged the motor and aimed the Discovery directly into the path of the oncoming Sorocaima, which was on its way to the North Korean port of Wonsan.

The tanker held ten million gallons of refined diesel, ready for use by the North Korean Army for almost every vehicle in their arsenal. With fuel embargoed by most other nations and having few refineries of their own, the increasingly belligerent North Koreans depended on regular diesel shipments from Venezuela, whose president was a personal friend of their leader. Without the fuel, the North’s armed forces would grind to a halt.

The Oregon could easily sink a ship of even the Sorocaima’s size with the weapons at its disposal, but the mission was more subtle than that. Not only did the Corporation refuse to sink unarmed vessels but there was no shortage of tankers or Venezuelan oil, so at best the shipment would only be delayed. Instead, Linda, MacD, and Mike were going to ruin the fuel on board the tanker, laying waste to a huge swath of vehicles in the North Korean military.

At the back of Discovery were six thermos-sized canisters, one meant for each hold on the tanker. The canisters were loaded with bacteria developed in secret by the Defense Advanced Research Projects Agency, or DARPA. Mutated from a strain of the anaerobic bacteria clostridium and dubbed Corrodium by the biologists who created it, the microbe multiplied easily in diesel, contaminating an entire tank once it was introduced. It was colorless and odorless, so the contamination was undetectable without laboratory testing.

The bacteria changed the composition of the diesel so that it would burn much hotter. When the tainted diesel was ignited in engines, it would cause them to overheat and seize up, resulting in a total loss. With luck, the Corrodium that they had injected into the holds of the Sorocaima would go on to infect the entire North Korean supply, rendering it unusable and destroying the engines of any vehicles into which the diesel had been loaded.

The hard part was getting the Corrodium into the fuel without being detected. If there was any suspicion that the diesel had been tampered with, the Sorocaima crew would test it and find out the problem long before it reached Wonsan. Once the North Koreans knew about the potential for bacterial infection, they would have every delivery of diesel tested for it. Linda and her team had to get the mission right the first time because there wouldn’t be a second.

The delicacy of the operation was also the reason for conducting it simultaneously with the Chairman’s recon mission. If they were done separately and the initial one in the sequence failed, success with the other operation would be in jeopardy.

Linda’s responsibility on this mission was to keep the mini-sub on-station while MacD and Mike climbed the side of the tanker with the Corrodium and delivered it into the holds using the ship’s own deck piping system.

But they couldn’t get on the ship while it was moving. Even if they could match the tanker’s speed, maneuvering the Discovery next to it and keeping it stable while MacD and Mike tried to disembark was a recipe for disaster. They had to get the Sorocaima to stop.

Disabling the tanker in any way was out of the question. It might be tugged back to port, instead of going on to North Korea, and investigators might realize the damage was intentional, prompting questions about who had done it and why. Stealth was the only option, and it had a side benefit as well. If the North Koreans blamed the Venezuelans for the contamination, it would make them less likely to trust their suppliers for future diesel shipments.

It was Max as usual who had used his engineering expertise to devise a way to get a tanker to stop without hijacking or damaging it.

The Discovery’s robotic arms cradled an apparatus the size and shape of a coffin, flat on the long sides, with watertight Plexiglas sealing the ends and an uninflated tube on top. A filament connected the object, which they called the beatbox, to a control system inside the mini-sub. When attached to the hull, the beatbox, which was equipped with a high-impact rotating hammer, would knock with each rotation of the propeller shaft.

No captain likes to be stranded in the middle of the ocean with a dead engine, so the mechanical systems are tuned and maintained rigorously to run at peak operating efficiency. If the engineer heard a pounding in the engine room that couldn’t be located, he would recommend that they stop the ship until the problem could be diagnosed. Of course, in this case there wouldn’t be a problem at all, and the onboard instrumentation would tell them that. Max estimated they would have thirty minutes before the engineer deemed the engines safe and cranked them back up.

“Hold on, boys,” Linda said. “We’re heading under.”

She flicked the joysticks expertly and dived the sub, maneuvering the Discovery so that it was below the path the Sorocaima would take. The rush of water being pushed by the immense tanker’s bow grew until it sounded as if the sub were a barrel floating toward Niagara Falls.

Using the onboard LIDAR, or light detection and ranging system, which relied on a series of reflected lasers that would re-create a three-dimensional image of anything they saw, Linda could see the tanker’s hull soar over them like a zeppelin drifting through the clouds.

Linda clicked on her on-screen control and the tube on top of the beatbox inflated until it made the apparatus neutrally buoyant. She retracted the robotic arms and then backed the Discovery away, unspooling the filament control wire as she did. She stopped when she was a hundred yards away.

The positioning was perfect. The beatbox hovered twenty feet below the centerline of the tanker.

The tanker’s gigantic single screw thrashed as it got closer. Linda would have to time this right. Too early and she’d get the beatbox too far forward of the engine room to be mistaken for a problem with the turbine. Too late and she’d get the beatbox chewed up by the screw or miss the tanker entirely. If that happened, there was no way the sub would be able to catch up and try again.

When the last hundred feet of the tanker passed overhead, she clicked another button, activating the powerful magnet on the beatbox. It flipped as the magnetized side was pulled by the steel hull of the Sorocaima. A loud bang signaled that the beatbox had made contact and was holding fast to the tanker only four feet from where Linda had been aiming.

The filament continued to feed out. She clicked another button and the hammer inside the beatbox started to pound away. She nudged the joysticks forward to the sub’s maximum speed so that they would be as close as possible when the tanker came to a stop.

“Keep your fingers crossed,” she said.

There was an agonizing wait as she looked for any signs that the tanker was slowing. A thousand yards of the filament had already played out. They had three thousand to go. After that, she’d have to cut it loose.

Another thousand yards came and went before she finally saw the unspooling of the filament slowing down.

“Good old Max,” she said.

“I knew he wouldn’t let us down,” Mike said, rechecking the pistol that he was bringing along as a precaution even though their mission was to avoid any contact.

“Looks like we’re going to have ourselves a cliff face to tackle,” MacD said, and assembled their climbing gear.

When the Discovery caught up with the now stationary tanker, Linda’s watch told her that they had twenty-five minutes left out of Max’s thirty-minute limit. She surfaced the Discovery next to the bow, as far as possible from the engine room and bridge, where the center of activity would be taking place right now.