Girdling the Earth are bands of deadly radiation, the Van Allen Belts. They form a prison, an egg shell that humanity can never pierce. Embittered, the human race turns inward. Psychic powers come to the fore. At first, the psychically endowed paranormals ("parries") use their gifts for a lark or for profit. Over time, the world comes to hate these deviants, forcing them into ghettos and isolated towns.
All except for the rare few employed by Fishhook, an agency that has opened up the stars through other means. Fusing technology and innate power, the "Fishermen" project their minds across the light years and explore other worlds. They bring back wondrous gifts of technology, which are sold in Fishhook-owned centers called "Trading Posts." The Fishermen encounter a riot of experiences: things of incomprehensible beauty, things of unspeakable evil. The most rigidly enforced rule is that the Fishermen must retain their humanity; any taint of alien, any hint of going native, and they are cloistered in a community that is, for all intents and purposes, a gilded cage.
All of which are just abstract concerns to Blaine, a veteran Fisherman, tourist of a hundred worlds, until the day he encounters the pinkness: a sprawling, shabby, impossibly old creature who tells him, "Hi Pal. I trade with you my mind..."
(see the rest at Galactic Journey!)