In many ways this classic two-parter reminds me of the classic TNG epic "Chain of Command". In both you have a first episode that functions as setup for a walloping conclusion, but stands up on its own merit.
The Garak-centric "The Wire" developed the relationship between him and Dr. Bashir, but also planted the seeds for Odo's interest in the mysterious "tailor". That emerges full-blown here, as Odo tears through Garak's lies even faster than the latter can weave them. There are some classic sequences here - Garak's interesting perspectives on human culture ("The Boy Who Cried Wolf" and Shakespeare's Julius Caesar in particular), Odo's eerie encounter with a mysterious Cardassian informant, Odo cutting through the elegant/pretentious wordplay of Cardassian spies like the B.S. it is.
Of course, the punchline comes in part 2.