"There's a good background for you, Stokely. It faces the lock, and I imagine you'll want to do the same." He swung the flashlight slowly around. There were several piles of boulders standing about, and Archer indicated two of them, each about 120 degrees from the first. "Evans and I can take those two positions. That way we'll form a triangle, each of us about 40 feet from the ship, and in plain sight of the others--that is, _if_ we develop that fatal glow. In any case, Stokely, I think you can depend on us staying put until we find out, since--" "And then what happens?" Stokely demanded impatiently. "How do we find out--without trusting each other? The whole set-up sounds silly to me!" "It's my life, too," Archer reminded him. "And in case you're in any doubt, I don't trust you, either. Here's the plan: As you know, all of us were exposed within a very few minutes of each other. That means, according to our late friend, the doctor, that in ten to 12 minutes from now--perhaps a few minutes longer--one or more of us should show the symptomatic aura. "Now there's the point: _one or more_ of us. There's an excellent chance we won't all show it. Allowing an adequate margin, the next 20 minutes should reveal who has the infection and who hasn't. I propose that at the end of that time each of us in turn announces, not which of the others shows it but simply whether he sees the aura at all. He doesn't tell whether one or both of the others shows it, but merely whether _at least one_ does." "What good would that do anybody?" asked Stokely glumly. "None, in itself. But you forget that all of us will be reporting. For instance, supposing Evans says he sees it, but I don't show it, or vice versa--two very distinct possibilities. Then you'd know that the only place Evans could have seen it--" "What if he were lying?" Stokely put in sharply. "That's the general idea in back of the whole scheme. He couldn't get away with it. If he said he saw it and didn't, it could only mean that neither you nor I showed it. In that case--which is one of the lesser possibilities, incidentally--I'd be led into the same error that you would. But it would then be very much to our mutual benefit to compare notes before taking any injection. "If he said he didn't see it, and either of us had it, the other would know he was lying. If we can't trust each other to tell the truth, we can't very well depend on each other to back up our lies--especially when there is everything to lose by it. If you knew Evans was lying about me, how would you know whether he was telling the truth about you?" "Now listen!" protested Evans, who seemed to be shivering as much with fear as with the cold, "you guys talk like you expected me to pull a fast one. Hell, it's complicated enough if we all tell the truth--don't worry about me!"