An epidemic is wiping out the Trailmen, cousin to the Cherie.
Terra sends Jason to find the source of the disease and a cure before it sweeps the entire planet....
What he learns is it was introduced by Terrans seeking to take the world for themselves.
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The call has gone out through the galaxy for telepaths - working or suppressed, to be trained by the Darkovans in an effort to supplement the surviving telepaths of Darkover, to fortify the blood.... and to save the foreign telepaths from madness.
Problem is, most of those over the age of 3 were already insane!

Although some books are loosely connected, having characters in common, they were written to be read independently and were written out of sequence. Part of the difficulty of knowing what to read, and in what order to read comes from that. The Planet Savers (1962) and The Sword of Aldones (1958) are two of the earliest novels MZB ever published, the first two published in the Darkover series, even though chronologically they come late. The Sword of Aldones was first conceived in MZB's teens in fact, and feeling the story deserved a more mature treatment, she rewrote it and it was published as Sharra's Exile. That's a much better book, and you should read it instead. The Planet Savers is short and entertaining, but barely indicates the potential of the series at its best. You get more a glimpse of that in the included short story, "The Waterfall," written about 15 years after The Planet Savers, after Marion Zimmer Bradley had greatly improved as a writer. As a Darkover fan, I'm happy to have The Planet Savers and "The Waterfall," but by no means is this the place to start reading the series and the novels included in this edition are among MZB's weakest books and not representative of the series at its best. (