Caption: Sisko and an older Jake
Caption: Sisko attempts to fix the warp core
Caption: Jake's future home
Caption: Sisko at a fateful moment
Season: 4 Ep. 2
Air Date: 10/09/1995
Decades into the future, an elderly Jake Sisko is visited at his New Orleans home by a young, aspiring author named Melanie, who is curious to know why he stopped writing at age 40. Jake reveals how he lost his father, Benjamin Sisko, when just 18-years old. The younger Sisko had gone along on the Defiant to witness a rare inversion of the wormhole that happens just once every 50 years. During the trip, Sisko was hit by a bolt of energy from the malfunctioning warp core, after which he dematerialized, eventually given up for dead by his anguished crew.
Months later, Sisko appeared in his son's room briefly, then vanished. The incident was dismissed as a nightmare until, after a few more months passed, Jake again saw his father. This time, he was able to touch him, and immediately summoned help. Sisko was taken to the Infirmary, where the officers realized his temporal signature had been altered during the warp core accident. But before they could save him, he dematerialized again, while his son watched helplessly.
For the next few months, Dax and O'Brien tried to locate Sisko, but were soon forced to abandon the station to the Klingons. Jake returned to Earth, became a writer, got married, and started to put the past behind him. Then, while Jake was in his mid-thirties, his father appeared in his home. This time, Jake was overcome with guilt, upset over doing nothing to help his father for all those years. So when Sisko dematerialized yet again, Jake became obsessed with getting him back. He abandoned his writing to study subspace mechanics, losing his wife in the process. But, after many years, Jake was prepared for his one chance to recreate the accident — the wormhole was scheduled to invert again. Reunited with a much older Defiant crew, led by Captain Nog, Jake returned to the scene of the accident, and wound up with Sisko in a subspace limbo. Unfortunately, the plan didn't work, and Jake was only able to spend a few moments with his father, who begged Jake to make a life for himself before it was too late.
The aged Jake finishes his account by presenting the departing Melanie with a collection of stories he's written to fulfill his father's wishes. He then reveals that Sisko is scheduled to appear — and Jake has finally learned how to save him. If he dies while his father is with him, the "cord" which has been pulling Sisko through time with his son will snap, springing Sisko back to the moment of the accident. Sisko arrives, stunned to learn that Jake has poisoned himself. But Jake tells his father that he wants another chance to go through life with his dad. He dies, and Sisko is suddenly back on the Defiant at the fateful instant. This time, he ducks before the bolt from the warp core strikes, avoiding the accident, and giving him a second chance at life with his son.