Things Past

Sisko, Odo, Dax, and Garak are found unconscious in their runabout. While Bashir attempts to revive their bodies in the present, Sisko and the others wake up on Terok Nor — the station's previous name — during the Cardassian occupation of Bajor. They look normal to each other, but everyone else sees them as Bajorans. Odo, who was once Terok Nor's Chief of Security, seems particularly agitated and anxious. They spot Odo's predecessor, Thrax, which indicates that they have gone back in time at least nine years. Two soldiers then haul away Dax.

While Dax learns she has been selected to be Dukat's "friend," Garak scans the group to determine their identities. Sisko is a Bajoran named Ishan Chaye. Garak is Jillur Gueta. He then scans Odo, who supplies his own name — Timor Landi. Odo awkwardly explains that Timor, Ishan, and Jillur were falsely accused of trying to assassinate Gul Dukat on the Promenade — and were publicly executed there.

They realize that this is actually seven years ago, and Odo had taken over for Thrax as Security Chief. Since they must get off the station before their pending execution, Sisko contacts the Bajoran Resistance. However, the attempt on Dukat's life occurs before they leave, and Sisko, Odo, and Garak are arrested.

In a cell, Odo tries to convince Thrax to investigate further, but he refuses. Dax escapes from Dukat, frees her friends and leads them toward Dukat's shuttle. Thrax blocks their path and a fight ensues where he is revealed to be a Changeling. the group moves on toward the airlock, but as they enter, they suddenly find themselves back in the cell, where a soldier tells them they will be executed in two hours.

Sisko realizes everything leads back to Odo. Thrax and Odo appear on the Promenade, watching as Sisko, Dax, and Garak are about to executed. Odo exclaims that he won't let this happen again. The scene changes, leaving Odo alone with his friends. Further down the Promenade, they see the execution, with Odo wearing Thrax's uniform looking dispassionately. A horrified Odo admits that he — not Thrax — allowed the innocent Bajorans to die. Odo then wakes up in Deep Space Nine's Infirmary. Bashir tells him that a plasma storm the runabout encountered caused Odo's mind to lock his friends into a version of the Great Link. Odo realizes that his guilt forced him to relive the incident and face his failure.