When an accident on the planet Golana sends Molly O'Brien through a mysterious vortex three hundred years into the past, she returns to the present eighteen years old with no immediate recollection of her previous life or her family.

Sisko is chosen to lead an invasion into Cardassian territory, ignoring a warning of impending doom if he leaves DS9 from the Prophets, resulting in fatal consequences for a member of the crew.