She had, gradually, come to type telepaths much as blood donors had once been typed on the mother planet. There were three basic types of telepaths: A--those who could _receive_ mental messages as delivered from all directions and distances, B--those who could not only _receive_ but grade the thoughts that came to them directionally and tune in or out selected thought waves as they chose, and, C--those who were capable of _projecting_ their own thoughts and impulses into the minds of others and possessed as well the capabilities of groups A and B. A types were almost a norm on Mars, Lynne had learned. In the sympathetic environment of the Red Planet, latent telepathy was at least faintly active in eight out of ten Earthfolk, The B’s were less common--only about three in a thousand Martians could _tune_ the messages their minds received. And only one in a hundred thousand was a C type. All in all, there were two hundred and seventeen telepaths at the Depot--two hundred and sixteen now that Juan Olsen was dead--and the variations among them was what complicated the problem. Curiously enough, the A’s could receive from the greatest distances, even though they couldn’t tune the messages unaided. But a B, linked with an A, could tune in from a further distance than a B working alone. Similarly, a C lined up with an A, could broadcast almost infinitely. On record was one contact with a spaceship far out beyond Pluto’s orbit. But human contacts were not the main purpose of the Depot. What the investigators were seeking was contact with alien life-forms, either on, or beyond Mars. If telepaths had been able to make contact with the aborigines that had so nearly destroyed them, it seemed reasonable to suppose that they should be able to make contact with other alien intellects. Apparently, judging by what had happened, they had done so. But what monstrous life-form had they contacted--and where was it located? For more than a Martian month, Lynne had been aware of a force--strangely stimulating--lurking just beyond range of her probing. She had, on two occasions, felt a sudden surge of power while working with Revere or one of the others, a power that flared up and faded quickly, leaving irritation in its wake. There had been a restlessness in the Depot atmosphere, a restlessness that had shown itself in such lapses as poor Rana’s childish drawing in the folio. Other C types had reverted now and then to basic nature--to ill-temper, to ridiculous practical jokes, to fits of melancholy, even to overindulgence in lichenwasser. “Angel, how about a drink? You’ve been sitting in a brown study for two hours now--and the color scheme of this room is baby-blue.” It was Tony, bless him, bringing her out of it.