Molly O'Brien disappears through a time portal.
This is an okay episode that includes decent character moments.
For me the plot unfolds in a mostly contrived way as it includes certain events that feel like they happen because the writers want to have their cake and eat it with painful emotional moments and happy endings. As some reviewers have correctly pointed out, the Federation is supposed to be an advanced, progressive society, which makes the treatment of Molly feel especially forced into the story to create the central dilemma.
I like the interaction between characters in various family situations. The O'Brien family, plus the likes of Worf, Jadzia and Odo are all used very well during interactions with each other. The Worf and Jadzia scenes in particular work well considering what happens in the season finale.
All actors are on good form, particularly Colm Meaney, who always impresses when the writers make his character suffer.