Almost a century ago, Captain James T. Kirk and the crew of the starship Enterprise first encountered the irresistible (and astonishingly prolific) lifeform known as the tribbles, resulting in one of the most unusual adventures in the annals of Starfleet. Now Captain Benjamin Sisko and the crew of the Defiant are transported back in time to that historic occasion, where Darvin, a devious Klingon spy, plots revenge against Captain Kirk. Using the seemingly harmless tribbles, Darvin attempts to destroy Kirk—but for the misplaced residents of Deep Space 9, saving the original Enterprise will be nothing but "tribble".