During the early 2330s, Sarah became possessed by a Prophet – a non-linear alien species which lived in the then-undiscovered Bajoran wormhole – in order to ensure she met and had a child with Joseph Sisko. As part of this plan, she owned a necklace with the phrase, in ancient Bajoran script, "Orb of the Emissary".
During this time, the Prophet inside her made sure that the necklace stayed in their house.
Eventually, the Prophet left Sarah, and, when she regained control of her body, Sarah left her husband and son without an explanation in 2333, as she did not really love Joseph but could not explain why she seemed to.
The despondent Joseph Sisko spent three years searching for her. He finally succeeded, but only a month after her death.
Joseph later remarried and never mentioned Sarah to his son as he grew up, who assumed his stepmother was his real mother.
Sarah Sisko was played by actress Deborah Lacey.