A girl's imaginary friend is more than it seems.
A young girl named Clara Sutter, lonely on the Enterprise, has an imaginary friend named Isabella. When the ship encounters a strange energy force in a nebula, Isabella appears in physical form, and Clara begins to depend on the friend. At first the visitor seems harmless, but the ship's systems begin to fail.
The episode is a quiet science-fiction story about loneliness and the way that children cope. Troi and Picard must decide how to deal with the alien presence, which is more than it appears. The story is a gentle one in the fifth season, and it shows the series' care for the families on board. It is a small drama with a tense final act.