Dax is assigned a trainee, and a proto-universe appears.
Dax is assigned to evaluate Arjin, a young Trill candidate for joining, who expects a harsh mentor like Curzon and finds Jadzia more relaxed. A runabout trip through the wormhole brings back a strange mass that turns out to be a tiny, rapidly expanding universe containing signs of life.
A plague of Cardassian voles adds to the trouble on the station. Dax pushes Arjin to think about what he really wants, telling him how hard Curzon had been on her. Rather than destroy the proto-universe, Sisko has it taken back through the wormhole, and Arjin pilots the runabout through the danger to release it.