“I’m sorry, Toller.” Gurra aimed the sunwriter at the approaching airship and the glass slats inside it clacked as he began to operate the trigger.

Toller hopped from one foot to the other as he watched for some evidence that the pilot was receiving and heeding the beamed warning. The ship drifted onwards, blind and serene. Toller raised his telescope and concentrated his gaze on the blue-painted gondola, noting with some surprise that it bore the plume-and-sword symbol which proclaimed the vessel to be a royal messenger. What possible reason could the King have for communicating with one of the Lord Philosopher’s most remote experimental stations?

After what seemed an age, his enhanced vision enabled him to discern hurried movements behind the ship’s foredeck rails. A few seconds later there were puffs of grey smoke along.the gondola’s left side, indicating that its lateral drive tubes were being fired. The airship’s envelope rippled and the whole assemblage tilted as the craft slewed to the right. It was rapidly shedding height during the manoeuvre, but by then it was actually grazing the cloud, being lost to view now and again as it was engulfed by vaporous tendrils. A wail of terror, fine-drawn by distance and flowing air, reached the hushed watchers along the shore, causing some of the men to shift uneasily.

Toller guessed that somebody on board the airship had encountered a ptertha and he felt a thrill of dread. It was a fate which had overtaken him many times in bad dreams. The essence of the nightmare was not in visions of dying, but in the sense of utter hopelessness, the futility of trying to resist once a ptertha had come within its killing radius. Faced by assassins or ferocious animals, a man could — no matter how overwhelming the odds — go down fighting and in that way aspire to a strange reconciliation with death, but when the livid globes came questing and quivering, there was nothing that could be done.