“Any idea what it’s like?” O’Brien asked, finding, to his surprise, that he was having trouble catching up to the little doctor.

“Uh-uh. I spent two hours with the microscope this afternoon. Not a sign. I prepared a lot of slides, blood, spinal fluid, sputum, and I’ve got a shelf of specimen Tars all filled up. They’ll come in handy for Earthside doctors if ever we— Oh, well. You see, it could be a filterable virus, it could be a bacillus requiring some special stain to make it visible, anything. But the most he was hoping for was to detect it—we’d never have the time to develop a remedy.”

He entered the control room, still well ahead of the taller man, stood to one side, and, once the other had come in, locked the door. O’Brien found his actions puzzling.

“I can’t see why you’re feeling so hopeless, doe. We have those white mice down below that were intended for testing purposes if Mars turned out to have half an atmosphere after all. Couldn’t you use them as experimental animals and try to work up a vaccine?”

The doctor chuckled without turning his lips up into a smile. “In twenty-four hours. Like in the movies. No, and even if I intended to take a whirl at it, which I did, it’s out of the question now.”

“What do you mean—now?”

Schneider sat down carefully and put his medical equipment on the desk beside him. Then he grinned. “Got an aspirin, Pres?”

Automatically, O’Brien’s hand went into the pocket of his jumper. “No, but I think that—” Then he understood. A wet towel unrolled in his abdomen. “When did it start?” he inquired softly.

“It must have started near the end of the lecture, but I was too busy to notice it. I first felt it just as I was leaving the mess hall. A real ear splitter at the moment. No, keep away!” he shouted, as O’Brien started forward sympathetically. “This probably won’t do any good, but at least keep your distance. Maybe it will give you a little extra time.”