Marque of Caine – Snippet 06

At this rate, statistical analysis indicated that the target would reach the other side of the island before the drones effected intercept. And if the target’s child–whose signal that was now nearing the air terminal–was seeking assistance, he would surely find and return with it long before then. That mission-failure condition would immediately trigger the drone’s self-destruct protocol, thereby minimizing forensically useful evidence.

The big drone’s self-learning analytics ran through higher-risk intercept options. Rise and maneuver to a point directly above the target, then attempt to descend through the jungle canopy? Contraindicated: despite increasing the risk of detection by both local law enforcement and any target-friendly assets that might be in covert overwatch, the vertical assault option still did not guarantee success. Observational data was indeterminate regarding the canopy’s obstructive characteristics, but radar showed it to be unpromisingly thick. Any significant delay during descent would certainly give the target ample opportunity to detect the drone’s audio signature and possibly inflict damage while it was vulnerable.

The self-learning system went further outside its optimal mission parameters, engaged less conventional subroutines: heuristic learning, historical examples, human prediction algorithms. All analyses produced the same result: return to the trail. It was the longer route by a factor of three, but its unobstructed flight path would allow the drone to eventually overtake the target. The only drawback was increased risk of detection by other humans: the risk variable that weighed most heavily against any autonomous departures from the precoded scenarios.

But no other option promised comparable speed and efficacy, and the risk was no worse than a pop-up attempt to effect an overhead intercept.

The two subdrones reversed, sped back toward the trail that twisted through the jungle like a serpent. The large drone followed at a distance of twenty meters.

*     *     *

Riordan had not come this way often enough to recall the subtle differences in the trees that signified he was nearing his goal. A surge in daylight–sudden and bright–triggered a shielding reflex with his hand. Which put him off balance just as he remembered that the small clearing was a half step below the jungle floor. He tumbled forward.

A faint sulfur stink hit his nostrils as his chest and cheek hit the slimy mud. Might as well get used to both. He pushed up on his arms, looked around. No sign of pursuit. The trail here was more overgrown than before: the hiking traffic had been low and the sightlines were more limited than usual. All to his advantage.

Riordan rose, looked across the small clearing, where a crevice almost bisected a wedge of volcanic rock that pushed through the foliage. It was the cavemouth he’d been heading for: a tapering spearhead of black shadow, two meters from base to tip.

Moving from rock to rock to avoid the mud, Caine quickly crossed to and entered the cave, tapping his wristlink three times for maximum illumination. As on his prior visits, the mud had pooled back into the cave itself: the morning run-off from Nevis carried dirt down the slopes and kept the ground wet.

The light from his wristlink picked out the walls’ most jagged protrusions: every inch was rough and irregular, like most of the island’s volcanic vents. He smiled.

Dimming his light, he felt for and found a short left-hand switchback tunnel that was more like a hidden alcove. He shone the light higher, saw the small natural ledge he’d found twenty months ago. Riordan reached up cautiously. It was a little close to the entrance for bats, but you could never be sure…

Fortunately, his fingertips brushed against smooth, dry plastic, not leathery wings and sharp teeth. Pulling down the bag, Riordan inspected its seal: still tight.

The contents–mostly communications gear–showed no sign of water damage. They had been left behind at the house that Richard Downing’s family used to own, just a few miles further south on the ring road. It was also where Elena’s brother Trevor had linked up with the ops team that he had led to Indonesia. Needing to travel light, they had left behind a small stash of equipment, the location of which Trevor had shared just before Caine began his voluntary exile on Nevis.

Caine had excavated the gear his first week there, but much of it had already been discovered by the implacable foe of all hidden tropical caches: water. Half of the electronics were ruined, as were the two handguns that might have proven handy. But spec ops teams carried lots more than guns and radios, and enough of the equipment had survived that Caine resolved to hide it in a safer, higher, drier place.

Just in case.

*     *     *

As Connor climbed down Booby Island’s stony northern flank, he heard a faint high-pitched growl cutting through the rising and falling surges of the windward surf. He scanned the sky directly over St. Kitts: nothing. But when he widened his sweep to the ocean, he detected a small dark blot far to the west, coming around the leeward bluff known as Nags Head. The blot grew larger, but did not move to the right or left.

Which meant it was heading straight for Booby Island.

Connor turned and swiftly clambered back up into the gnarled trees, the midday sweat suddenly cool on his body, the grip of the sloop’s pistol slick in his hand.

 *     *     *

As the main drone and its two small reconnaissance platforms neared the target’s transponder, they slowed: the signal was coming from a mass of what seemed to be solid rock. One of the subdrones swung wide, flanked the volcanic spur which protruded into the clearing. Ladar scans confirmed the AI’s hypothesis: there was a cave opening.

The main drone updated and assessed the summative operational situation. The discus-sized drone that had followed the signal heading south indicated that although it was slowly gaining on its target, it might not effect intercept before draining its battery.

The third subdrone was still tracking the signal that was now following Nevis’ rocky eastern coastline. There, the difficulty was not speed but unexpected terrain obstructions–obstructions that the target was courting to frustrate and extend the pursuit.

But it was precisely that similarity between those two targets–that they were attempting to evade, rather than elude–which suggested that the signals were emanating from decoys. A human would not settle for evasion or mere delay. A human’s survival instinct required nothing less than complete escape or complete concealment. Which meant that the signal in the cave was almost certainly the one emanating from the actual target.

The large drone advanced its subdrones to further assess the environment: the cave mouth was large enough to admit a human easily. Scanning the internal layout from outside was impossible without a sophisticated densitometer, a device many times the mass and volume of the drone itself. The geographic feature into which the cave penetrated was otherwise solid rock, rising up a further three meters and terminating in a wildly overgrown shelf that was itself an extrusion of the larger, higher slopes of volcanic rock. If there was any means of flying upwards to achieve vertical descent into the cave, ladar scans did not reveal it.

The drone’s AI chewed at the problem, quickly reduced it to a single operational option. Send a subdrone into the cave to acquire a 3-D ladar rendering of the layout, and, in the course of doing so, attempt to close with the source of the transponder signal. The main drone would follow relatively close behind. If the target emerged to destroy the subdrone or flee, it would be eliminated. The other subdrone would maintain a rear watch and remain in reserve as a potential replacement for the first subdrone.

Obedient to the main drone’s summons, the lead quadrotor abandoned its fruitless survey of the overgrown upslope ledge and made for the cave mouth.