Synopsis: An alien criminal, attempting to prolong his life, hides his consciousness inside the mind of a station crew member.
Memory Alpha Summary: Mr. Mystery dislikes overdone tropes.
Review: How many times has Star Trek done the whole alien body snatcher plot? It’s just not that interesting, no matter how they dress it up. The mystery is not a mystery as the teaser more or less reveals the climax forty minutes earlier.
The subplot of Odo having to get along with another Starfleet officer is necessary but rather mundane, with the exception of Odo trying to resign because a reasonable human being had a difference of opinion with him.