"They may be robot-controlled," suggested Phil Maxwell, the gunner on the side of the car toward the forts. "Any sign of an entrance, Ann?"
"Nothing but the gunports," replied the girl in the turret.
"Don't fool with them, John," said Commander Wallace, who was tuned in from the ship on the car's communications system. "If they're robot-controlled, they'll be booby-trapped. Move out of range and continue with your exploration."
Two days later, the car emerged from the desert into comparatively fertile country. The four explorers found a broken concrete highway and followed it between rolling, treeless grasslands. Near dusk, they saw smoke on the horizon—and ran into a roadblock.
A segment of the highway had been thrown up into a ten-foot wall, barring their progress. Over the edge of the wall, the muzzles of heat-guns pointed at them as they brought the car to a halt some distance away. John got the commander on the car radio.
"We could swing around it, but we don't know whether they have vehicles that could outrun us," he reported. "And my conception of our mission is to establish contact."
"That's right," agreed Tom. "But stay in the car until you get a friendly reaction. Then you're on your own—and I'm afraid you're expendable, John."
John switched on the loudspeaker and made overtures to the roadblock. After a moment, a lone figure stepped around the edge of the mound of earth and concrete and approached the car slowly. The man was dressed in the drab, baggy uniform of a professional soldier.
"If you come in peace, leave your vehicle and identify yourself," called the soldier. "You will not be harmed."