"Past Tense" is a two-part episode from the third season of science fiction television series Star Trek: Deep Space Nine, the 57th and 58th episodes overall and the last episode to air before the premiere of its spinoff, Star Trek: Voyager. It is also the first episode of Star Trek: Deep Space Nine to not feature any scenes on the DS9 space station, except for the opening credits.
In the episode, a transporter anomaly accidentally sends Commander Sisko, Dr. Bashir, and Jadzia Dax back in time to a pivotal moment in Earth's history. The episode received critical acclaim for analyzing U.S. social issues in a science fiction context, but also for addressing various societal issues such as homelessness, poverty, and technology.
Broadcast
This installment of the Star Trek science fiction television show Star Trek: Deep Space Nine aired in two approximately 45 minute episodes on syndicated television in the United States. The first episode aired on January 2, 1995 and the conclusion (Part II) aired on January 9, 1995.
Plot
Part I
When Commander Sisko, Dr. Bashir, and Jadzia Dax beam down to Earth from the Defiant, an accident occurs and they materialize in San Francisco in the year 2024.
Sisko and Bashir are found by a pair of police officers, who believe them to be vagrants and warn them to get off the streets. They are escorted to a "Sanctuary District", a walled-off ghetto that is used to contain the poor, the sick, the mentally disabled, and anyone else who cannot support themselves. Sisko realizes they have arrived just days before the "Bell Riots", a violent confrontation in the Sanctuary District that Sisko recalls as a watershed moment in human history. Dozens will be killed, including a man named Gabriel Bell, the leader of the demonstration. Bell will become a hero because of his self-sacrifice while protecting hostages, and public attitudes toward the disadvantaged will begin to change. Unable to find a building to sleep in, and unwilling to get involved with a nascent movement to air the residents' grievances for fear of altering history, Sisko and Bashir live in the street.
Meanwhile, Dax is found by a prominent businessman, Chris Brynner, who arranges accommodations for her. Later attending an affluent party as his guest, she realizes that Sisko and Bashir may have been taken into the Sanctuary District and persuades him to help confirm her suspicions.
Within the district, a fight breaks out when Sisko and Bashir resist attempts to take the ration cards they have been issued. A man who comes to their aid is killed, and Sisko and Bashir discover after the fact that he was Bell. Sisko quickly realizes that due to their presence, the course of history stands to be radically changed, since Bell is no longer present to safeguard the hostages in the historical narrative. The district residents begin to riot, and one group storms the processing center and takes the employees hostage. Sisko and Bashir return there, and Sisko assumes Bell's identity and takes leadership of the revolt in an effort to keep the hostages safe.
Back in the 24th century, the crew left on the Defiant, Major Kira, Odo, and Chief O'Brien, lose contact with Earth as all traces of the Federation suddenly vanish; Bell's death has radically altered the timeline. O'Brien calculates several possible time periods in which Dax, Sisko, and Bashir might have arrived, and Kira and O'Brien begin transporting to one period at a time in order to search for them.
Part II
Sisko tries to ensure that no one gets hurt during the standoff, while at the same time understanding that Bell must die at the end of it. He makes demands to the governor, insisting they be given airtime to express their grievances. He wants the Sanctuary Districts closed and their residents to be given opportunities to earn an honest living.
Dax watches news coverage of the riots from Brynner's office, knowing Sisko and Bashir are caught in the Sanctuary District and are in danger, and heads down to find them. She sneaks along an underground sewer line, but she is caught and delivered to the employment center to explain herself. Sisko and Bashir meet with her in secret to explain why they must stay until the crisis is over. She sneaks back out, certain that Brynner will be able to order a terminal activated at the processing center so that the leaders of the revolt can tell their stories and have them broadcast worldwide, which was the main force that turned public opinion against the Sanctuary Districts and led to their abolition.