By midafternoon it was gone, leaving only an expanse of mud that dried and cracked under the glaring sun.
Klev twittered anxiously at this latest development.
"He says the Martians have discovered what we did, and set the vora to pumping the water away again," Susan translated.
"No matter. The ship is on the way by now."
As evening approached Nick wedged a large boulder firmly into the mouth of the tunnel, placed his back against it and announced his intention of sleeping there.
"At least we'll know if they come after us," he said.
Klev nodded approval.
But the Martians made no attempt at reprisal for the humans' interference, as they were too busy preparing their attack on the camp.
Next morning truckloads of drilling equipment rolled out from camp, and soon a dozen rigs were boring through the sand and underlying rock. Floodlights were erected and the drilling went on day and night.
But the space beacon did not flame again with the news that the water had vanished. Power was too precious.