“The Wavists were challenged to demonstrate just how a wave traveling at lightspeed could traverse twenty-five light-years in just twenty years. But they rationalized that the inciting beam emanated from some third point, twenty years closer to the first afflicted colony than to the second. They waited eagerly for a third colony to be struck, so that triangulation could locate the origin. And in turn they challenged the Particlists to explain why no member of the moon-based quarantine party had contracted the illness, since many had been exposed before the full danger was understood. And why the chill showed no abatement whatever prior to its fixed termination, if it were really mutating its steady way into oblivion. The reply was that the quarantine experts had been exceedingly careful at all times, as proven by their ability to avoid contagion by the chill; and that the chill itself abated even though the symptoms displayed by man did not. When the causative virus weakened so that it dropped below the threshold of effectiveness, the body’s natural defenses were able to repel it.

“Five years later both theories had their trials. A third colony was struck—but because its medic had been too busy publishing the learned tracts required for tenure and promotion to keep up with the medical literature, he failed to recognize the chill until several deaths had occurred. Infected colonists by this time had visited five other planets, including Earth itself. Moon station had been bypassed. Yet not a single case appeared outside the stricken colony, though the sick travelers cooled and died in public hospitals. The Particlists strained to explain the paradoxes, and could not. One of the victims had happened to be a popular call girl who continued her practice until her clientele complained of her literal frigidity. She died; the clients lived. The particle theory had been exploded.

“The Wavists pounced on the third coordinate with enthusiasm and triangulated for the fabled source. The third point was seventy-three light-years from the first; location was elementary. A ship of experts was dispatched. It found only empty space. If there had been a source, it had departed long since. And the disgruntled Particlists were quick to point out that a number of unaffected colonies lay between that so-called source point and the affected planets. How had those other colonies been missed? Was the wave discriminating? But in any event, the particular beam to strike the third colony could now be extrapolated. Volunteers planted themselves squarely in it—and were not affected. There was no beam, and the Wavists had been swamped.

“Time passed and the mystery deepened. Additional colonies were devastated, yet any victim removed within a day of the first symptom recovered promptly. If the chill were a contagious disease, why did time and location set such capricious limits? If it were a wave, why did so many escape?