Shadowplay

Odo and Dax try to solve the mystery of a alien planet whose inhabitants are disappearing without explanation.

A little girl's mother is one of those who has disappeared.

Odo befriends her. She is fascinated with the fact that he is a changeling. She does not believe he can change shape because he does not like to do it unless it is nessecary.

Dax and Odo discover that everyone is really a hologram.

Dax can repair the faulty photonic projector, but has to turn it off first. That is when they also discover that this one old guy is really human. He wants to leave the planet, but Dax and Odo convince him that the holographic people are real enough to them, and that they ought to be real to him.

The little girl is his grandaughter.

He agrees to stay but asks that niether Dax nor Odo tell the townspeople that he is human and thus, not one of them.

Dax fixes the projector and switches it back on; all the people plus the ones who vanished earlier return.

As he is leaving, Odo turns into a top to show the girl that he is really a changeling.

Superb episode! I remember seeing it when it first aired
early in 1994 and this is the one that got me into being a big fan of the show.

"I offer you a Vulcan prayer, Mr Suder. May your

death bring you the peace you never found in

life." - Tuvok.