By Paul de Anguera.

“Which way should we go now, sir?” a Guest Star asked the First Mate anxiously.

“To the left — down those stairs,” the First Mate directed. They were searching the ruins of Musawwarat-es-Sufra for Professor Hentrack, who had stolen Cilantro’s letter under the ruse of deciphering it. But the plazas, dusty avenues and crumbling staircases seemed to go on forever, and he had no idea where to look. So he tried to show his decisiveness and leadership to best advantage by making frequent, arbitrary changes of direction as they plunged deeper into the maze. Soon they were hopelessly lost.

But Sanders, the Unix Kernel, was fascinated. “Here we are in the heart of Kush, a 3,000-year-old empire, and all we see is total desolation! It’s hard to imagine this as the civilization that overran Egypt in 731 BC. Nothing can live in this harsh environment today — only the humble lichen clinging to these ancient stones.” He plucked up a bit and held it by the thallus. “Peltigera egyptus,” he mused. “The lower Nile is the only part of the world where you’ll find it.”

“Be careful how you hold that,” Sir Hillary warned. They stepped through an arch and entered an avenue flanked by columns. The Guest Star stumbled as a flagstone pivoted under his feet. They heard a mechanical clunking noise, and a nearby stone column toppled on him with a thunderous crash, partially burying him (or completely burying him, if you are watching this at home).

“Everybody stand still!” the First Mate ordered. They froze, even though it was midday in the desert, while he turned to survey the mosaic of paving blocks which separated them from the arch by which they had entered. Some were booby- trapped; but which?

“If I may make a suggestion,” Sir Hillary offered, “the problem here is to avoid stepping on the flagstones which have been tampered with. Now, some of these stones are covered with growths such as this,” he added, indicating the sample which Sanders was holding. “So, we can assume that they have not been disturbed. But other stones are clean.”

The First Mate thought this over, and ordered:

“Walk lichen Egyptian!”