.... Following the arc set by "The Emissary" and "The Sins of the Father" (two great episodes of "Star Trek: The Next Generation"), "Reunion" is a thrilling and moving Klingon/Worf-centered episode, marking Jonathan Frakes' second directed episode.
Suzie Plakson makes her return to the series as K'Ehleyr, Worf's ex - not only is she perfectly cast and extremely solid in this episode but she is also a total babe. The character's relationship with Worf features a lot of laughs as well as some very compelling moments. "Reunion" is also notable for Worf meeting his and K'Ehleyr's son Alexander, a character that would continue on through "The Next Generation" and "Deep Space Nine." This story line (hence: the "Reunion") is very compelling as Worf comes to terms with his new found fatherhood.
The personal themes of family surrounding Worf's role in the story are great but "Reunion" also sees a pretty thrilling political arc. The plot is closely tied to that especially of "The Sins of the Father," so one is greatly benefited by seeing that episode first, with Picard once again being drawn into Klingon politics - this time the stakes are much higher than they were before.
"Reunion" is, for my money, one of the best episodes of the series' fourth season.