Defiant has Commander William Riker apparently arriving at DS9, flirting quite a bit with Major Kira before he steals the USS Defiant and reveals himself to be none other than Will Riker's transporter accident duplicate Thomas Riker! Sisko is forced to team up with Gul Dukat in order to track the Defiant down before Riker starts destroying Cardassian outposts. Kira is kidnapped and on board, and can't understand why Riker is instead taking the Defiant to a system in Cardassian space of no consequence in order to follow up on rumours of a mystery Cardassian shipyard. This is all set up for events in later episodes involving a mysterious secret Cardassian fleet under the control of the Obsidian Order. It was very engrossing, and the idea of Dukat and Sisko both forced to work with each other in some quite tense scenes are very memorable. There was an intention to bring Thomas Riker back to Deep Space Nine, but it ultimately was never followed up on by the writers and this was a shame. Unlike his appearance in Enterprise, Jonathan Frakes actually made Deep Space Nine better and it would have been interesting to see Thomas Riker taking on a different persona.
