Dax starts suffering from severe hallucinations and black-outs. Concerned, Sisko and Bashir take her back to the Trill homeworld where they hope to find an answer to her plight. Jadzia's body seems to be rejecting the symbiont. Soon it becomes apparent that the Trill Symbiosis Commission authorities are hiding something and are prepared to sacrifice Jadzia's life to stop the truth from coming out.

Lisa Banes (Dr. Renhol)
Jeff Magnus McBride (Joran Belar)
Nicholas Cascone (Timor)
Harvey Vernon (Yolad)

• Dax learns that one of her symbiont's hosts, Joran Dax, was a murderer. He killed three people. The Symbiosis Commission tried to hide the memories from Jadzia Dax.
  
• The Trill symbionts are bred in pools located in the underground Caves of Mak'ala.