William T. Riker arrives on Deep Space Nine and proceeds to charm the crew, especially Major Kira. She takes him on a tour of the station and its new ship, the Defiant. Once aboard, he draws a phaser and stuns her, fakes a warp-core breach, and steals the ship.
Back on the station the crew realizes it is not Will Riker but his duplicate Thomas Riker, who had been created in a transporter accident and stranded on a planet nine years earlier and was rescued about two years ago (see "Second Chances"). He is suspected to have since joined the Maquis, and the heavily-armed Defiant in their hands now poses a serious threat to Cardassian forces. Commander Sisko is faced with the challenge of retrieving the Defiant intact while avoiding an incident with Cardassia that may start a war. He agrees to travel to Cardassia Prime to cooperate with a Cardassian operation led by Gul Dukat to hunt Riker down.
After infiltrating Cardassian space and attacking an outpost, Riker takes the Defiant to the Orias system, which he believes contains a secret shipbuilding facility. When Sisko analyzes Riker's movements and realizes his true target, Dukat, believing the system to be barren and of no value, orders his ships to intercept. His Obsidian Order observer Korinas, however, warns him that any ship (Cardassian or otherwise) that approaches the system will be destroyed. As the Order is strictly forbidden from possessing military equipment of any kind, Dukat becomes suspicious.
The Defiant manages to outrun its pursuers into the Orias system, but is confronted by several more Cardassian ships appearing from the system itself. On Cardassia, Dukat's displays show the ships as well, but he determines they are not under the control of Central Command. With the Defiant trapped between the two fleets, Sisko arranges a deal with Dukat: In exchange for the Defiant's sensor logs of the system, the Defiant will surrender to Dukat's lead ship and will be returned along with its crew to the Federation, and Riker will be sentenced to a Cardassian labor camp rather than to death. Kira persuades Riker to accept the terms. The opposing ships approach the Defiant and its Cardassian escorts, but abort the confrontation and return to the Orias system. Riker beams to the Cardassian ship, leaving Kira in control to return to the station.
