For longer than he could remember, Stan had heard excited predictions about how nanomachines would transform the world, create wealth out of garbage, build new cities, and save civilization from the dire prospect of ever-dwindling resources. They would also scour your arteries, restore brain tissue to youthful vigor, and mayhaps even cure bad breath. In reality, their uses were limited. The microscopic robots were energy gluttons, and they required utterly well-ordered environments to work in. Even to lay down a uniform crystalline antenna, molecule by molecule in a nutrient-chemical bath, would require attention in advance to every detail.

Carefully, he used Alex’s equations to adjust the design, teasing the cylinder into just the right shape to send delicate probes of radiation downward through those fiery circles of hell below, in search of an elusive monster. It was blissfully distracting work.

When the explosion struck, the initial wall of sound almost knocked Stan off his stool. Booming echoes reverberated down the rocky galleries. A scream followed, and a hissing roar.

Men and women dropped tools, rushing to a bend in the cave where they stared in apparent horror. Alex Lustig plowed past the throng toward the commotion. Stan stood up, blinking. “What… ?” But none of the running techs stopped to answer his question.

“Get a ladder!” someone cried. “There’s no time!” another shouted.

Negotiating a maze of pipes and wires cluttering the floor, Stan finally managed to nudge past a rank of gawkers and see what had happened. It looked at first as if a steam line had broken, jetting hot vapor across a wall festooned with gridlike latticework. But the wind that suddenly hit him wasn’t searing. It knocked him back with a blast of bitter cold.