Rodney paused. "We might not recognize one."
Martin urged him on. "You know what a man-hole cover looks like." He added dryly, "Use your imagination."
They reached the metal wall at the end of the avenue and paused again, uncertain.
Martin swung his flashlight, illuminating the distorted metal shapes.
Wass said, "All this had a purpose, once...."
"We'll disperse and search carefully," Martin said.
"I wonder what the pattern was."
"... The reservoirs, Wass. The pattern will still be here for later expeditions to study. So will we if we don't find a way to get out."
Their radios recorded Rodney's gasp. Then—"Martin! Martin! I think I've found something!"
Martin began to run. After a moment's hesitation, Wass swung in behind him.