The Gate to Futures Past — Julie E. Czerneda

Betrayed and attacked, the Clan fled the Trade Pact for Cersi, believing that world their long-lost home. With them went a lone alien, the Human named Jason Morgan, Chosen of their leader, Sira di Sarc. Tragically, their arrival upset the Balance between Cersi's three sentient species. And so the Clan, with their newfound kin, must flee again.
 
Their starship, powered by the M'hir, follows a course set long ago, for Clan abilities came from an experiment their ancestors -- the Hoveny -- conducted on themselves. But it's a perilous journey. The Clan must endure more than cramped conditions and inner turmoil.
 
Their dead are Calling.
 
Sira must keep her people from answering, for if they do, they die. Morgan searches the ship for answers, afraid the Hoveny's tech is beyond his grasp. Their only hope? To reach their destination.
 
Little do Sira and Morgan realize their destination holds the gravest threat of all....