This is another psychological mystery that involves Deanna being put upon, following up on "Violations" and probably others I can't think of.
There's a fair amount of creepiness and tension built throughout. The direction of the episode is subtle enough that, though we can tell at times that Deanna is hallucinating, the line between dream and reality is blurred.
Ultimately, though, this episode's success rides on two factors - your interest in Deanna's neuroses (somewhat overplayed at this point), and to what degree you find her romance with Worf to be convincing. At this point in the series, I really could not care either way.