As his cellmates grinned, Tom's eyes roved over their faces. One man--wavy-haired with penetrating dark eyes--seemed oddly familiar. Why? Suddenly the answer hit Tom like a flash. He resembled Streffan Mirov, the brilliant Brungarian rocket scientist who had tried to oust Tom's expedition from the phantom satellite Nestria. Playing a hunch, Tom said to him, "You know what your government does to rebels and bunglers, Mirov." The man stiffened and paled. "We have not b-b-bungled!" he stuttered angrily. "Shut up, you fool!" their leader shouted. CHAPTER VI THE CAISSON CLUE "Captain Smith" had leaped to his feet, quivering with anger. But it was too late. His cellmate, by answering to the name of "Mirov," had given away their nationality! Tom and Ames exchanged grins of triumph. "No doubt you recall what happened to Streffan Mirov," Tom went on, pressing his advantage. "Or should I say the _late_ Streffan Mirov? Our last report was that he had been tried and condemned by your own government. Perhaps you can give us news of his fate?" The wavy-haired prisoner's eyes blazed with hate. "Grin while you can, Tom Swift! Because of you, my brother Streffan is now serving a long prison sentence! But I, Dimitri Mirov, will get revenge!" "You blame Tom Swift because your brother botched his job of claiming the satellite Nestria by force and fraud?" Ames taunted. "Our space friends moved that asteroid into orbit around the earth," Tom added. "We claimed it by right of first landing. Even your own leaders couldn't agree to Streffan's crazy scheme to destroy everything." Dimitri Mirov lost all control and burst into a volley of guttural Brungarian abuse. "I warn you, Swift!" he choked. "Jailing us will not make you safe--or your projects, either!" A blow to the head from "Captain Smith" sent Mirov reeling back against the wall. "Fool! Maybe that will quiet you!" the pilot snapped viciously. "You have said too much already!" "Let's go, Tom," said Ames. "We've learned the information we came for." The prisoners could only glare in baffled rage through the cell bars as Tom and the security chief turned their backs and walked away. "Nice going, Tom," Ames murmured. "Your hunch certainly paid off." Chief Slater added his congratulations when he heard how Tom had trapped Mirov into disclosing his identity. Both Tom and Ames were grave as they drove back to the plant. Neither took Mirov's threats lightly. Tom pondered another angle. Were the Brungarian rebels perhaps responsible for the attempted theft of the Jupiter-circling missile? Ames was inclined to think so. "Moreover," he forecast, "it's a cinch they haven't thrown their last punch. I'll pass the word to the FBI and Central Intelligence." After lunch Tom flew to Fearing Island with Bud, eager to tackle their interrupted job of rooting the space plants into the undersea silt beds. Zimby Cox, a sandy-haired, freckle-faced jetmariner, volunteered to pilot a motor launch for them.