Hoping to spend some quality time with his son, Sisko takes Jake on a survey of a Gamma Quadrant planet. Quark and Nog come along—Nog as a friend and partner in Jake's science project, Quark to suck up to Sisko in a poor attempt to convince the commander to let him sell merchandise on the station monitors. The pairing of Sisko and Quark is at the very least lively, and some of the Federation/Ferengi polemics that arise are actually relevant.
While on this planet, Sisko and Quark encounter and are promptly imprisoned by the Jem'Hadar—the menacing foot soldiers of the nefarious Gamma Quadrant organization called the Dominion. Apparently, the Dominion considers ships coming through the wormhole as violation of their territory.
"The Jem'Hadar" is "comic book DS9" in many ways. This isn't nearly as substantive as most of second season DS9. The Dominion is large and foreboding, and the plot consists of mostly action scenes and a prison-break premise. But this is good comic book DS9. It's fun, but it's also pretty intense at times, especially when a Jem'Hadar soldier visits the station and supplies Kira with a list of ships the Dominion has destroyed—along with news that they have decimated the New Bajor colony in the Gamma Quadrant. (Nana Visitor's performance sells the scene more than anything else.)
Meanwhile, Jake and Nog attempt to pilot the Runabout back to the station themselves, with little success. The idea of "teenagers flying the ship" is utilized for some great comic payoffs—Jake and Nog have always been fun to watch when they get in over their heads. The episode ends with the best battle scene the series has attempted to date. A Jem'Hadar kamikaze that destroys the Galaxy-class USS Odyssey is quite visceral. The episode is mostly high adventure and comedy, and it works well. (And stuff gets blowed up real good, too.) With the introduction of the Dominion, the series adds yet another element to its canvas which will fuel many stories to come.