Afterward, as they stood in the control turret of the _Libra_, watching a sober-faced Rick Norton plot the landing that would bring new life to the Ionian colonists, swift retribution to the fomenters of the uprising, Bud Chandler whaled his comrade's back enthusiastically. "Guy," he said, "in words of one syllable, you're terrific!" "That's not one syllable," grinned Mallory. "All right, then, you're a lallapalooza! But how the blue asteroids did you get onto the fact Smith was the guy?" Dan said, "It came to me almost too late. It had been worrying me subconsciously ever since I had to--" here he flushed--"had to arrest Lady Alice. I knew that someone had, in conversation with me, said something that didn't ring true. And when Wilmot was killed for having discovered the truth about Smith, I suddenly remembered what it was. "The night before we got the message from Lunar III, assuring us that Kreuther was behind the revolution, Smith had mentioned to me, quite casually, that he suspected there were on the _Libra_ 'espionage agents of the Kreuther forces.' What he was attempting to do, of course, was ally himself with us in order to divert suspicion. But he tipped his hand by that little slip of the tongue." Lady Alice smiled. She said, "Well, you're not awfully smart. Any of you. I knew he was the spy as soon as I heard the message from Earth." Captain Algase interrupted, "Yeah, that message! I'm going to raise an assortment of hell about that. Causing us to arrest the one person on board we could really trust." "And all," smiled the girl, "because of one, small, chemical symbol that you misread. Oh, yes, I understand now. I've seen the original. Bud--you went to the Academy, didn't you?" "Why--why, yes." "Your professor there must have been quite an old man. I mean your chemistry prof." "He was. Ancient. But what has that got to do with it?" "Everything. He taught you the old, the original chemical symbol for the element samarium. 'Sa.' The more common symbol, the generally accepted one, is 'Sm.' Now you see what a great difference that one little error makes in the meaning of the message. You read it: "'Lane warns Lady Alice, cabal spy, now on _Libra_. Captain saith intensify protection of new secret ray.'" "And it should have been read," broke in Dan Mallory, understanding at last, "'Lane warns Lady Alice cabal spy now on _Libra_--Captain Smith! Intensify protection--' and so on. It was a warning _to_ you, not about you!" "Exactly. Naturally, I was--well, indignant when I was placed under arrest. Afterward, I began to think it a good idea. Confined to my quarters, guarded, I would be completely safe. But unfortunately Captain Smith guessed, when I was arrested, that _I_ was the bearer of the formula. So he killed my guard, seized the skiff, and kidnaped me.