ed condition, served to bring him back to his
former health. The Venerians seemed glad to have it thus: asleep, he
did not disturb their activities.

* * * * *

When he had awakened from his first period of natural slumber, he had
received a terrible shock. His left arm was gone, amputated at the
shoulder. Strangely, the wound had healed while he slept, probably the
result of the Venerian doctoring, so there was no pain: but the shock
had been terrible.

After he had recovered from the effects of that shock, he had resolved
to make the Venerians pay for what they had done. And then he had
realized that the inhuman brutes must be destroyed for a greater
reason: unless he interfered, he believed that they would carry out
their intention of destroying all human life.

As the weeks passed by, while strength was returning to Parkinson, he
learned in a general way what the invaders were doing. They were
engaged in developing vast quantities of microbes to be spread over
Earth. When these were ready, a great amount of fine dust that the
Venerians had brought with them, was impregnated with the bacilli.
This was then taken up into the tower, where, as Parkinson learned
later, it was blown out through the four tubes that spun around the
tower's top, to drift through the air--to enter human bodies--to
destroy life.

The Venerians worked with the cultures and impregnated dust without
protection of any sort: evidently they were immune to the disease.
Later Parkinson learned that he was likewise immune; they had rendered
him to after trying the germs upon him.

Gradually the bacteriologist's health returned--so gradually that his
captors seemed not to notice it. He was glad of this, for their
vigilance had relaxed, and he did not want it renewed. Even when he
was as strong and well as ever, he spent much time in bed, shamming
illness. And when he could do so without danger of detection, he kept
a close watch upon the three, waiting for a time when he would be
entirely alone.

* * * * *

At last his opportunity came. The three Venerians rose to the surface
together, leaving him in his room, to all outward appearances, asleep.
But sleep was far from him at that moment; he had been watching.

Shortly after the sphere had vanished up the shaft, Parkinson emerged
from his room. For a moment he surveyed the circle of doors: then he
shrugged his shoulders. They all l