gered by the increased salinity and by info from GloPos navsats, undergoing the transformation into upstream silicrobes. Separating from their partnered water molecules (which continued out to se a a s of yore), the upstream silicrobes made a coherent U-turn and headed back. Without H2O partners, they needed a virtual channel only half the size of the downstream one to make their way back to Machine Lake and resorption. Upstream speed was 80 percent of the downstream current.

Except today.

The last chunky frondtree fell to Dos Santos's flashlight-machete with a sound like a watermelon hitting the floor from table-height, and sticky juice propelled by xylemic pressure sprayed his face and millipore suit. Then he stepped out of the jungle and onto the staymown vetiver turf of River Seven's upstream bank.

"Peej– suit bladders are now full with purified water, and any further dermal suit-contamination will have to be exosonically evaporated."

"Fine, fine," said Dos Santos absentmindedly, his entire concentration, basal and add-on, devoted to his ailing wide River.

The bipartite line of hyperfluid was dramatically sick.

Consider the more distant downstream side.

From its border with the upstream virtual channel all the way to the far bank, the downstream two-thirds of the River was

a stagnant dove-grey stripe. The deactivated silicrobes, apparently still remaining in suspension, now no longer contributed any motion to the flow and in fact hindered the water molecules from resuming even their old basal speed. The downstream waterway, until so recently an efficient Riverroad upon which millions relied, was now a turbid slurry.

Dos Santos looked to the left, downstream, but focused his gaze on the nearer third of the River, the upstream channel.

This portion of River Seven was still functioning. Being composed of pure silicrobes, it was matte black in color and stood out sharply, its border still cohesive, from the downstream mess. But this normal appearance was misleading, and Dos Santos knew-

With a sharp intake of breath, the River Master spotted it.

The failure wavefront.

He watched helplessly as the killer disinformation propagated swiftly upriver, soon reaching his position and passing unstoppably on.

Behind it, silicrobes went offline by the hundreds of trillions. The black stripe instantly began to extend irregular fingers of darkness into the downstream portion of the River, silicrobes flowing "backwards," and from greater concentration to lesser as the now-unthinking River-formerly considered an actual entity of Turing Level One-attempted to homogenize itself according to dumb physics.

"Damn. Damn, damn, damn!"

Momentary hopelessness washed over Dos Santos. He had dedicated his life to Riparian Admin, out of a love for

these great semiliquid, semi-intelligent transport machines. For the past fifty years, he had worked self-sacrificingly on the Rivers of the world, the large and the small. River Eight (the old Volga), River Three (the old Mississippi), River One-Oh-Four (the old Ganges), River Twenty-Nine (the old Nile), even River One (the old Amazon)-First as apprentice, then as journeyman, finally as Master, he had lovingly tended these sinuous creations of humanity that snaked across the domesticated globe, carrying mankind's freight and travelers, hosting its recreations, bathing its pilgrims. And never in that time had he experienced such a thing as this horror: the death of one of his charges.

It felt like he imagined the death of the never-met pairbond proxy and hypothetical zygotes he had never permitted himself to indulge in would have felt. There was a hole in his soul.

Anger and a determination for revenge replaced the hopelessness. Dos Santos would make someone pay.

And River Seven, he vowed, would live again.

He advanced to the edge of the banking, which sloped away steeply to the River, a forty-five degree stretch of crumbly red clay, and scrambled down.

A rush of small dislodged pebbles tumbled down to the River surface and sat atop the high-density gel-like silicrobe liquid, each rock centered in its own surface-tension dimple.

The kibe sounded alarmed. "Peej Dos Santos, you do not intend-"

Dos Santos reached the marge of the River and squatted down. The pebbles were drifting downstream.

"Quiet! If you want to be useful, prepare to analyze some telemetry."

After peeling off both gloves, the River Master inserted his hands into the stagnant silicrobe soup.

The shimmerstats boiled with metagrafix in the corners of his eyes, fed by the subdermal mycotronix digiface sensors in his fingertips. Tapping the feed, the kibe added its verbal interpretation.

"It appears that the River has been contaminated with a dose of high-velocity instruction ribozymes based on the standard stepdown routines, but with subtle alterations that are not readily decodeable. The silicrobes are merely offline and apparently undamaged. If we could denature the invader, it would be a simple matter to restart the River-"

Dos Santos stood. "We'll have to do it fast, though, and that means getting to the facilities at Machine Lake. Not only do we have to worry about the possibility of further attacks, but there are system constraints as well. Eventually, the 'crobes are going to drop out of suspension and settle to the bottom. A restart under those conditions would be chaotic. We'd kick up enough particulates to clog the whole delt a a nd probably kill off all the lifeforms as well. And if the mixing of upriver and downRiver 'crobes continues, the vortices that'll form on a reboot will be orders of magnitude larger than normal-"

The kibe interrupted. "Speaking of vortices, Peej, here comes a Vortifish Hunter right now!"

The coracle glittered nacreously, catching glints of African sunlight, an upturned halfshell with rippled, purpled rim. (Its original seedstock, highly modified of course, had been the chambered nautilus.) Large enough to hold two basal humans, it now contained only one sophont, a cynocephali wearing a loin covering of plaid clothtree fabric.

Originally the cynocephali-or Anubians-had been bred and released only along River Twenty-Nine, the old Nile. Part tourist attraction, these bipedal dog headed sophonts had been designed to occupy a new top niche in the food chain. So successful and popular had they proven that no River today, some ten Anubian generations later, was without them.

The furred humanoid splice stood at the rear of its tiny craft, the tiller that controlled the steering jets in its paw. It sailed midway down the former upstream channel whose black syrupy components were now uselessly and slowly heading downstream with all the rest.

The small vessel was plainly bearing toward Dos Santos.

As the craft drew nearer, Dos Santos could make out further details, including grown-bone spears racked across the bow. And as the lone sailor expertly beached its craft, Dos Santos recognized the tattoon icon beneath the skin of one canine ear as the mark of the Hyena Tribe of Vortifishers.

''Peej Human!" barked the splice, showing sharp teeth webbed with saliva. "Our River dying!"

At that moment, the kibe announced, "Incoming transmission via Global Telesis for the River Master."

"Accept."

The pleasant female voice of his Fon apprentice, Isoke, whom he had left behind in Lagos, sounded in Dos Santos's right ear like a beacon from a saner world.

"Norodom! The saboteurs have been pinged and popped! They were greenpeacers calling themselves the Izaak Walton League. Only ten human members, but they managed to kill several Rivers and disrupt half the world's gross shipping tonnage! Dai Ichi Kangyo has just issued an estimate of five billion time dollars worth of loss. But the crickcops and the IMF blueboys are certain they've slagged them all! You shouldn't have to worry about another disruption."