Kid: Is it true that you can kill someone just by looking at him?
Worf: Only when I am angry.
On board the Defiant, the DS9 crew find a planet with a strange energy barrier. They manage to penetrate it and find a settlement of several thousand people who claim to be their descendants. They are told that when they try to escape the energy barrier to leave, they will be thrown two hundred years into the past and the Defiant will crash. Sisko is forced into a difficult choice; if they succeed in escaping, all these thousands of people will be wiped from existence; but if they do not, they will never see their homes or families again.
This episode contains examples of
- Always Save the Girl: The future Odo changes the Defiant's course heading at the last minute, which saves Kira's life at the cost of erasing the entire settlement.
- Applied Phlebotinum: Discussed and averted. The "two Defiants" escape, in which one would escape and the other would crash and create the colony was a typical Star Trek "Deus Ex Phlebotinum" solution allowing the crew to Take a Third Option was completely false, forcing the crew into an actual hard decision. Kira even Lampshades it during her You Can't Fight Fate speech, feeling like it's "cheating".
- Better to Die than Be Killed: The Sons of Mohg tell Worf they'd rather commit suicide than have a "dishonorable" death by simply vanishing from reality.
- Defiant to the End: The colonists harvest their crops despite knowing they'll be non-existent. Worf tells the Sons of Mohg it's "a battle against time."
- Embarrassing Old Photo / Noodle Incident: Yedrin convinces Sisko by beginning a story about a certain exotic dancer.
- Funny Background Event: Jadzia can't help but grin because she also knows the secret story.
- Everybody's Dead, Dave:Sisko (after they somehow clear the barrier): Scan the surface.Kira: No sign of the settlement. Or the inhabitants. Everything's gone.
- Heroic Sacrifice: Future!Odo believes he is doing this so that Kira may live, but subverted as said sacrifice doesn't just cancel out his own existence, but thousands of innocent people. Odo does argue that thousands of people wouldn't exist because the crew didn't return safely to Deep Space 9, though it's doubtful that's his reason for changing the flight plan.
- Love Confession: Once the Defiant arrives at the planet, a 200-years-older Odo wastes no time in beaming up to the Defiant and making one of these to Kira. Doubles as a Wham Line.Odo: I love you, Nerys. I've always loved you.
- Mandatory Line: Quark briefly appears as a computer program teaching math to the colony's children, something Dax says he would be well-suited for.
- My Greatest Failure: According to Yedrin, the Defiant becoming trapped in the past was this for Jadzia."Because of me, Kira died, and 48 people were stranded here. You don't know what it was like to live with that. For years, Benjamin, every time I looked at you, all I could think about was Jake and how, because of me, he would never see his father again. Eventually, I had to accept the fact there was nothing I could do to change things; I couldn't bring Kira back. All I could do was look to the future, Benjamin, and make sure that we survived here—no matter what."
- The Needs of the Many: Examined from several different perspectives.
- Nice Job Breaking It, Hero!: Jadzia admits she was in such a rush to make a discovery that she didn't properly scan the barrier surrounding the planet.
- Offscreen Breakup: Kira. After dating First Minister Shakaar for about a year, they visited a shrine and got a prophecy saying they weren't meant to be together.
- Proud Warrior Race: More like Proud Warrior Philosophy. Worf's descendants have split off from the main colony to live a more martial lifestyle in keeping with Klingon traditions of honor and courage, but humans can also join (and have) if they prove themselves worthy. They all call themselves "the Sons of Mogh."
- The Reveal: Yedrin didn't sabotage the plan to have the Defiant fulfill destiny — Future!Odo did.
- Sadistic Choice: The crew can use their future knowledge to save themselves and Kira, but if they do, they'll erase the 8,000 settlers on Gaia.
- Set Right What Once Went Wrong: The entire episode involves the crew deciding whether or not to do this: Do they use their new-found knowledge of the future to avoid the temporal barrier and save Kira, or do they follow the same course of events as before, crash-land on the planet, and save the existence of their descendants living on Gaia? In the end, the crew decides to do the latter, but the 200-years-older Odo, who can't bear the thought of losing Kira again, changes the course heading at the last minute so the Defiant misses the temporal barrier, effectively setting right what once went wrong.
- Shrouded in Myth: Worf to the crew's descendants.Gabriel: Are you the son of Mogh?
Worf: Yes, I am.
Gabriel: Is it true you can kill someone just by looking at them?
Worf: Only when I am angry.
Bashir: Apparently that planet is full of Bashirs!Kira: That's why I'm staying up here.
- As is Bashir, who delights in his own fame.
- Status Quo Is God: Invoked at the last minute, in a particularly tragic example.
- Take a Third Option: What Yedrin proposes - use the anomaly to create two Defiant ships - one that escapes, the other crashes. Unfortunately, it's a lienote which Jadzia catches on to.
- Timey-Wimey Ball: Two examples. First, in the original timeline, the Defiant lands on the planet, the crew learns about the colony, and then they knowingly take off knowing they'll hit the anomaly and be sent back in time. They do, they crash, they have children, their children have children, and eventually these become the people that the Defiant crew encountered before. But the colony shouldn't exist until at least one time through the loop, because it didn't come from anywhere; the colony causes itself to exist. This is, of course, impossible. Second, and much worse, the loop is sabotaged by Alternate!Odo. By preventing the Defiant from crashing, Alternate!Odo prevents himself from ever existing. This is, of course, impossible. Then again, none of this is in an actual alternate timeline, and in the present, so there would be no reason the crew would "forget" about the colony. Of course, this ''is Star Trek''.O'Brien(s): I hate temporal mechanics.
- What the Hell, Hero?: Kira lays a huge one on Odo when she finds out Alternate!Odo sabotaged the plan to crash the Defiant so Kira could live at the expense of 8000 colonists.Kira: I can't believe it! 8000 people?!Odo: He did it for you, Nerys. He loved you.Kira: That makes it right?!
Odo: I don't know. He thought so.
- You Can't Fight Fate: Kira strongly believes this. So much so that when a plan to "split" the Defiant crew into two seems like a "cheat". She's almost relieved that the plan is false, and decides she'd rather die than erase 8000 colonists from existence. Meanwhile, O'Brien is willing to "cheat his way back to the station". Worf responds by accusing Miles of being "afraid to face your destiny."