Star Trek: Deep Space Nine S05 E14 In Purgatory's Shadow (1)

"At the edge of the Final Frontier, the Universe's greatest mystery is about to unfold."

Stardate: Unknown. A coded message from the Gamma Quadrant leads Garak to believe his mentor, Enabran Tain, is still alive. He and Worf seek him out, only to discover something much worse: a Dominion invasion fleet poised to attack the Alpha Quadrant.