
fissure, the crawler's winch motor was reeling in the cable. It arrived with a faint jar at the opposite side
and, without pausing, inched up and over.
Sitting erect behind her instruments, Zael was charting the mineral deposits she passed over. It was a
satisfaction to her to find they were rich enough to repay surface mining. The cities could make almost
anything out of anything, but they needed a primary source: they had to have metals.
Methodically, she spiraled outward from the bubble house, charting a region no more than thirty miles in
diameter. In the unpressurized crawler, it was not feasible to take in a larger area.
Laboring alone, hour after hour under the unchanging sky, she identified the richest lodes, marked them
and established routes. Between times, she ate and slept in the bubble house, tended her necessary
plants, serviced her equipment. Out of her armor, she was slender and spare, quick in her movements,
with the harsh, thin-lipped comeliness of her people.
When her chart was made, she rode out again. At each marked spot, she dropped two widely separated
poles. Self-embedding, each pair generated a current which ionized the metals or metallic salts and would
slowly deposit pure metal around the cathode. Eventually the concentration would be such that the metal
could be sawed out in blocks for convenient loading.
Only then did she turn her attention to the traces of shaped metal that clung here and there to the rocks.
They were fragments, for the most part, such as were commonly found on cold satellites like Mimas and
Titan, and occasionally on stony asteroids. It was not a matter of any importance; it simply meant that the
planetoid had been inhabited or colonized at one time by the same pre-human civilization that had left its
traces throughout the solar system.
But she had been sent to see whatever was to be seen. Her real work was almost done; she
conscientiously examined the traces, photographed some, took others for specimens. She beamed
regular radio reports to Gron; sometimes, five days later, there would be a curt acknowledgment waiting
for her in the printer; sometimes not. Regularly she made the rounds of the poles, testing the
concentration of metal. She was ready to replace any faulty poles she might find, but the occasion did not
arise; Gron equipment seldom failed.
The planetoid hung in its millennial arc. The sky imperceptibly turned around it. The moving spark that
was the escape shell traced its path, again and again. Zael grew restless and took the crawler on wider
explorations. Deep in the cold crannies of the mountains, she found some metal constructions that were
not mere fragments but complete works—dwellings or machines. The dwellings, if they were that, were
made for some creature smaller than man; the doorways were ovals not more than a foot across. She
dutifully radioed this information back to Gron and received the usual acknowledgment.
Then, one day the printer came to life out of season. The message read, I AM COMING. ISAR.
The ship would be three months slower than the message. Zael kept her calendar, rode her rounds, her
starlit face impassive. Above her the escape shell, unneeded now, made its monotonous passage over
and over. Zael was tracing the remnants of a complex of surface structures that had miraculously
survived, some half buried, others naked to the stars. She found where they led, in a crater only forty
miles from her base, a week before the ship was due.
In the crater was a heavily reinforced globe of metal, dented and scarred, but not broken. As Zael's light
shone steadily on it, a sudden puff of vapor went out; the globe seemed to haze over briefly. Zael peered,
interested: the minute warmth of the light beam must have thawed some film of frozen gas.
Then it happened again, and this time she could see distinctly: the jet escaped from a thin, dark seam that