In the third season episode "The Die is Cast", Tain came out of retirement to lead a joint operation between the Obsidian Order and the Romulan Tal Shiar. Their goal was to send a combined Cardassian-Romulan fleet into the Gamma Quadrant to attack the Founders of the Dominion and Tain recruited his former protege Garak to help him. However, the operation was doomed from the start: the fleet had been infiltrated by a changeling and the Founders had evacuated their homeworld before the fleet arrived, leaving a fleet of their own behind to wipe out the Tal Shiar and the Obsidian Order. Tain was believed to have perished during the battle, but had in fact been taken prisoner by the Dominion and placed in an internment camp.
In the fifth season episode "In Purgatory's Shadow", Tain had sent a coded message to Garak on DS9 informing him of his survival. Garak, accompanied by Worf, ventured into the Gamma Quadrant to find Tain, but the two were captured by the Jem'Hadar. After being taken to Internment Camp 371, they found that Tain was there too and that he was dying from a heart condition. With Garak knelt over his deathbed, Tain told Garak to escape and take vengeance against the Dominion for him. Garak agreed on the condition that Tain acknowledge him as his son and the two reminisce about the only day during Garak's childhood when Tain told him he was proud of him. He then slipped away quietly.