"This must have been their primary station," said Russ thoughtfully. "No matter what they seek to channel from the Sun on other planets, it is from here that the first and strongest diversion of solar energy must have been coming. This station may have been the last constructed--the final link put into place. And for that reason, they installed an alarm." "Ah," said Lockhart, "even if they did, would it necessarily have destroyed the station? After all, they would normally have figured on repairing whatever went wrong." "It seems to me," said Burl, "that the red flash itself didn't start the destruction. There was a delay--must have been several minutes--before it started. Could it be, that what was alerted was a watcher?" "Where?" said Boulton. "There was no place for a watcher to be in that station. We saw no sign of it." "Maybe deep underground?" suggested the engineer, Caton. "They might have living quarters a few miles underneath." "Highly unlikely," said Russ Clyde. "It would still be too hot, and, remember, these people plan to incinerate Mercury and the inner planets. They must be from the edge of the system. The delay may be a valuable clue to that. It would take time for a remote control station on another planet to see what was happening and take steps. If you can figure out exactly how many minutes and seconds elapsed between the flashing of the red bulb and the blowup, we could work out the approximate distance." But, unfortunately, the time could not be judged that accurately. Neither Burl nor Boulton had had time to look at his watch. They hung over the cold side of Mercury for several hours more while the two astronomers figured their next move. When the orbits had been determined, the _Magellan_ turned its massive wide nose away from the Sun toward a gleaming white disc that dominated the dark skies of outer space. With full power on, they pushed away from the littlest planet and began the long fall toward the Sun's second planet, that which some had considered to be Earth's veiled twin, Venus. There was a matter of thirty million miles to cross, and the crossing would be made fighting the pull of the Sun all the way. Caton and his men had spent the wait on Mercury working on the great generators in the powerhouse nose. They recalibrated the output and corrected it from the records kept during the flight inward. Now they were confident of its ability to drive the ship away from the Sun. Coming in, they had not been sure what their A-G drive would do and could do. Going outward they knew just what to expect.