This was the showdown, the decisive battle. Her being imported to Mars had been a step in the duel between the invisible aliens and the Communications Integration of the red planet, headed by Rolf Marcein and his telepaths and other department workers. Unless the aliens were stopped and stopped now there would be no holding them. Earthfolk on Mars were becoming increasingly telepathic and telepaths were the prey of the invisible foes. Lynne _knew_ somehow, from the thoughts of the aliens, that they had been growing steadily in strength since the arrival of the Earthmen on their planet, that after a creepingly slow revival for decades they had finally snow-balled to sufficient power to make open attacks upon human brains laid bare for telepathic communication. They longed to renew the lost pleasures of the flesh through possession of human bodies. Rolf and the scientists had learned something that afternoon from Lynne's twin, something about the nature and life-form of the attackers that had hitherto been concealed from them. They were moving to the attack themselves--and it was of vital import to them that Lynne should now get through with the message that would reveal this true nature. She tried desperately to reach Rolf--and when this effort failed to think of Mother Weedon or even plump Tony Willis engaged in amorous sports--but the keynote of the alien attack had been altered from suggestion of sensation to outright mental attack. Instead of bribery or blackmail through pain, she was being given sledgehammer treatment. But she _had_ to get her message through. Without her knowledge of the nature of the aliens Rolf would use faulty weapons against them, would lose precious time, time that might prove decisive for the survival of Earthmen on Mars. Despairing, knowing she could not hold out much longer against the attack with her mind open, Lynne summoned reserve powers she did not know she possessed and swept the planet's surface with her thoughts, seeking Rolf. Her love for him, her fear for Revere's ultimate fate, her affection for her new comrades--all combined to help her make a final superhuman effort. Yet for awhile it seemed that even this despairing try was destined to defeat. The floor was beginning to swim before her eyes when at last she reached Rolf, got him, lost him, got him again. With darkness closing about her she poured out her information, her theory, her surmises. Faintly at last she felt Rolf's Crehut! _The multiple bodies on the visual screen we thought were ghosts--of course they're the survivors, rather than the near-humans! Thanks million, honey, we'll know what to do now. Hold on out there--help is on its way._ But Lynne could hold out no longer. She felt the invisible attackers come pouring through her weakened mental barriers--her last remembered vision was of the floor rising rapidly to strike her. She turned her face away just before it hit.