Razor's Edge

The fourth book in Lisanne Norman's Sholan Alliance long-running science fiction series of alien contact and interspecies conflictCarrie and Kusac-she a human telepath, he a Sholan one-have together formed a bond stronger than all the differences between their two races. They have survived the political manipulations of both their peoples, as well as successfully walking the Fire Margins, journeying into the past with Kaid, the third member of their Triad, and returning with shocking revelations about the Valtegan enemy and the ancient Cataclysm that transformed Sholan society.
  But the price of breaking with tradition comes high, as does the ongoing protection offered by the military. And now Carrie, Kusac, Kaid, and T'Chebbi must undertake a rescue mission to the distant world of Jalna to save present-day Sholans and humans who have been trapped there, as well as a Sholan pair from the age of the Cataclysm.   What they can't foresee is that the Valtegans planted the seeds of destruction on Jalna long ago, transforming the locals into a dangerously unstable race and threatening the telepathic powers of Sholans and humans alike.