Captain Benjamin Sisko (Avery Brooks) notifies Lieutenant Commander Jadzia Dax (Terry Farrell) that a group of Trill scientists will be arriving soon at Deep Space Nine to perform experiments related to wormhole physics. The Trill are a species of humanoids, some of whom host a sluglike symbiont implanted into them. The symbionts live far longer than the hosts, and are moved into a new host when the old one dies. Jadzia is the eighth host of the Dax symbiont. Sisko tells Dax that the head scientist is Lenara Kahn (Susanna Thompson), and offers to grant Dax a leave of absence while the Trill scientists are aboard, but she turns it down. Upon Dax and Kahn's first meeting, Major Kira Nerys (Nana Visitor) notices that they are very familiar with each other; Dax tells her that Kahn used to be her wife. Dr. Julian Bashir (Alexander Siddig) later explains to Kira that previous hosts of the Dax and Kahn symbionts were married to each other, but Trill are forbidden from reassociating with partners and lovers of past hosts.