Lynne and Lao Mei-O'Connell and most of the rest of the citizens of Barkutburg listened attentively while Rolf told them the full story. The trouble, it seemed, was caused by the fact that the Earthmen had brought electricity back to Mars. "These creatures were forced to discard their corporeal bodies to survive on a planet as dead as this one," he went on. "Their food is electricity and they'd been existing on a starvation diet for thousands of years, until _we_ got here." "It's strange they never tried space-travel," said Lynne. "I don't believe their philosophy admitted to such a materialistic solution," Rolf replied. "They must have progressed like _farb_ in the spiritual direction to be able to discard their bodies at all. Probably couldn't manage it both ways." "That makes sense, Rolf." Lao nodded, looked at Rolf with an appeal she could not put into words. He understood, told her, "Your Revere is going to be right as _purt_. I know what you must have thought when Lynne gave you the message she got about what we were doing to him. I tried to conceal it for that reason but this young lady is too _farbly_ strong telepathically to shut her out. I'm sorry I had to make him suffer but he understood. And I wasn't going to damage him permanently. "We--that is, some of Tony Willis' bright young men, have managed to improve the necro-recorder so that it is no longer destructive of the mind of the usee. They'd been working on it against time--and against just such a situation as arose recently, when we were finally able to get Revere off duty for a bit." "Thanks." Lao Mei-O'Connell said the word gratefully. "It's been rough on you," Rolf told her, "but nothing like as rough as if our little friends got control of all the telepaths." "What did they feed on that made them strong?" Lynne asked. "Electricity," said Rolf. "Just because we couldn't make it work in open circuits doesn't mean we haven't tried. They got enough from our efforts partly to restore themselves--from such efforts and the leakage of our closed circuits. They were always sopping it up. "But we didn't even know what they looked like, though we had our suspicions. They figured to be survivors of the dominant species on the planet before it dried up--but Revere's test this afternoon gave us our first doubts. We were still up a tree when Lynne got her message through. That _did_ it! "But it was touch and go. I grabbed a space-ship to get to Lynne, then took a pinnace. If we hadn't managed to get the anion guns ready tonight I think we'd have been licked for all our knowledge. Now we've got _them_ licked. They can still raid our electricity once in awhile, but it's going to cost them." That was about it. Lynne got up and went outside in the chill Martian night to smoke a skinless cigarette. A little while later Rolf came out and joined her. He slipped an arm around her again, hugged her, said, "_Purt_, isn't it?"