"No form of lateral electronic communications functions reliably on Mars," he told her bluntly as if admitting a fact he hated to mention about the planet he loved. "Don't ask me why--it's just so, that's all. _Crehut_, do you think our best scientific brains haven't tried? They believe the thinness of the atmosphere and the resulting weakness of the Martian Heaviside Layer has something to do with it. We get messages from Earth and the other planet-stations clearly and, with the ato-reduced time lag, in a matter of seconds." "And you have to use telepaths to transmit and receive?" She was almost incredulous but her mind informed her he was telling the truth without reserve. "Whatever we can't heliograph or send over wire cables," he said unhappily. "And the climate of Mars is rough on cables. Above the ground the winds snap 'em. Underground they rot or the _czanworms_ eat through them. Now do you begin to understand?" "A--little," she replied hesitantly, unable to maintain her entirely justified anger against his sincere appeal. "But what about this threat--this madness? What is it?" "We don't know." His face was shadowed. "There may still be life-forms on Mars of which we know nothing--or perhaps manifestations of those we thought safe that are dangerous. But something apart from atmosphere or weather or diet or drink is creating insanity. And it seems to be affecting our telepaths rather than others. Maybe our telepathic minds are more open to whatever the influence is. I don't know." His expression turned grim. "I've never allowed them--it--to affect _me_." All at once she remembered the nightmare, the being alone in the crystal tower, the crowding in upon her of unseen things that whispered dreadful alluring suggestions, the sense of panic. She began to understand it with growing certainty. Lynne said, "My brother--Revere--he's one of those who's been affected, isn't he?" He hesitated, evidently felt the probe of her questing brain, nodded reluctantly. He said, "Your brother is one of them. The _purt_ of it is we don't dare send him back to Earth." "I understand." She shuddered, felt a reassuring hand on her shoulder, added, "He's mad, isn't he." It was statement, not query. "I'm afraid so--at least part of the time," he replied. "But don't worry. We have marvelous clinics on Mars. Once we get him to one of them there's a good chance of a cure." "You mean he isn't getting care now?" she asked, shocked. Rolf shook his head, replied, his voice low, "Not yet--not until you replace him. That's how short-handed we are. We've lost too many the last few months. And there simply aren't any replacements. That's why I rushed to Earth when I heard about you, why perhaps I used unscrupulous methods to get you to come. There are less than a million people on all of Mars."