After rejoining his former Cardassian mentor, Enabran Tain, Garak helps him in a joint mission with the Obsidian Order and the Romulan Tal Shiar. Tain has masterminded a plan to destroy the Founders — Odo's people, who rule the Dominion — and their homeworld. Tain, along with Colonel Lovok of the Tal Shiar, leads a fleet of cloaked Romulan and Cardassian ships into the Gamma Quadrant, commanding them from their Romulan Warbird. Garak is told to question Odo, who is being held prisoner aboard Tain's ship. However, Odo says he knows none of his people's secrets. On the station, Sisko learns of Tain's mission, and is warned by Starfleet's Admiral Toddman to prepare for retaliatory attacks by the Jem'Hadar.
Fearing Odo is aboard one of the Romulan ships, Sisko and his officers, including Security Chief Eddington, defy a direct order from Toddman and take the Defiant into the Gamma Quadrant to search for Odo. Soon afterward, the ship suddenly and inexplicably decloaks, leaving them vulnerable to attack by the Jem'Hadar, the Dominion's soldiers. Meanwhile, as Tain, Garak, and Lovok head for the Founders' planet, Tain urges Garak to interrogate Odo and learn if his people have a secret defense system. Garak agrees, but finds himself conflicted.
On the Defiant, Eddington confesses to sabotaging the cloaking device, under orders from Toddman to prevent pursuit of Tain's fleet. Back at the Romulan ship, Garak interrogates Odo using a device that prevents him from changing his shape. Odo insists he is not hiding anything, but Garak persists, and Odo begins to literally dry up and fall apart. Unable to watch Odo's excruciating agony, Garak begs him to talk, and Odo reveals his secret — he wants to rejoin his people. Shaken, Garak deactivates the device and lets Odo finally morph into liquid form.
Garak claims that Odo knows nothing, and Tain orders Odo killed. However, Lovok and Garak convince him to spare Odo for later Romulan study. The fleet then reaches the Founders' planet and opens fire, destroying part of the surface, but there is no change in the life form readings. Garak discovers their ships have been lured into a trap — the planet is actually deserted. As he explains, their vessels are suddenly surrounded by 150 Jem'Hadar ships.
The Jem'Hadar attack, and Garak takes advantage of the chaos to escape and rescue Odo. Surprisingly, Lovok helps them get to their Runabout and reveals he is actually one of the Founders. His people learned of Tain's plan and encouraged it in order to bait the Obsidian Order and Tal Shiar into annihilation. Lovok tries to convince Odo to return home, but he refuses. Forced to leave behind Tain, Odo and Garak escape on their ship, and the Defiant rescues them from the Jem'Hadar assault. The Romulan/Cardassian fleet is destroyed as the crew returns to the Alpha Quadrant, barely escaping with their lives.