Leading the oddest troupe their planet had ever known, Ice-Driller detected nothing. It was open water for as far as one could hear. Only his projected sound image of a distant black smoker could be heard inside the curtain of silt, but that was losing opacity. The murk was settling at a predictable angle, and although updrafts occasionally prolonged the softness, it had approached the limit. They would be soon visible. A sound below, probably just a ping, hit their weakening countermeasure. The game was up. The beam of sound struck them and The Object. In a moment, the sender would see the pattern in the static.

“Faster.” Ice-Driller whispered.

The receiver of the sound beam, an enemy soldier, was confused for a moment. The sonar image looked like a giant fuzzy sea slug. That enemy sent another beam of sound back at the center of the mass.

“Get ready,” Ice-Driller said to all his crew. “Wait for my call.”

A moment later, a cry of alarm rang below. It was a simple noisemaker, but was effective in alerting those below.

“Trigger! And swim! Now!” Ice-Driller said. He grabbed Study-Up and swam as fast as possible. The last thing he heard was the same sonopictorial image from Sand-Stirrer and Thermal-Rock on both sides of his head.

The Probe had received conflicting data: identical sonar images from different sides of the craft. It wasn’t exactly the same, of course; the machine’s incredible precision measured oddities in distance and tonality between the two sources, but the images matched with greater than 99% similarity. An obstruction to port and the same obstruction to starboard. The probe assumed with high probability errors in data reception. That data was then categorized as ‘bad.’ It was a death sentence for data.Earth had trained the deep neural network to discover and troubleshoot all types of bad data (spoofed data, strange echoes, and anything real or imagined). It activated one failsafe event, a subsystem to throw out that which was confusing and collect new, good data. This failsafe was the large ping to receive good data. The clarion cry for fresh good data to blow away the bad.

>

The expected image returned. The craft was safely above the seafloor and no problems detected.

> Another burst was sent from the backup sonar.

Lights turned on and cameras filmed, but its backup visual system detected no obstruction.

Ice-Driller had whited out.

His mind was full of stars and wavy lines. Decapods are self-deafening, so when they trigger their own their sonar organ shuts off for a sliver of a moment. Intense sounds nearby can also trigger the self-deafening measure as a protective adaptation, but the Object had a tone and frequency that decapods did not automatically deafen.

Sound and image were a jumbled roiling mass of white with giant dots of black and danced around Ice-Driller’s field of view. He realized one tentacle was still holding on to something… another arm… then he remembered Study-Up. With another arm, he held on tighter and tapped out a message.

She tapped back.

As soon as he recovered his senses, he yelled back out “Trigger! Again!”

>

He heard the same image fractions of moments before another deafening whiteout. This time he was more prepared and clutched his sound melon with two tentacles to desperately dampen the high frequency vibrations. It did little good.

Fullness and noise surrounded his mind.

When his senses returned, the first thing he understood was another call from far away. It was almost like the noisemakers or claxons used in the military.

Something is ahead.

Someone is ahead.

Many are ahead.

He could still feel Study-Up clenching him. Ice-Driller tapped out another message to her:

Spatial sense returned, and he grasped the situation. A school of large fish was in front and above them!

“Get them,” someone said, and there was the call of an allied noisemaker.

It was a detachment of swordfins from Deepvent!

He cried out, “We’re friendly to Deepvent! Help!”

The swordfins were domesticated war-fighting mounts that soldiers would ride into battle. Fast and aggressive, they could skewer an enemy with their long pointed bill. Most had metal saw teeth attached to them. Ridden by the defenders of Deepvent, they had heard the peculiar sound and responded to the pursuing enemy below.

Ice-Driller continued to guide The Object forward, and now he heard that the friendly line of battle below, a major counterattack, was taking place to free the path to Smallseep.

Below, he could sense a wave of soldiers roiling over the lines into the rocky terrain, looking for enemy soldiers. The swordfins swept around, impaling any free-swimming enemy that had fled up.

Counter-noisemaking and other echolocation jamming muffled the echoing cries of death and made a horrid cacophony in his mind. He pinged forward and saw the unmistakable sharp edges of the city’s buildings.

They finally arrived.

Now the impossible portion of their epic: stopping the war.