Sisko tells two men from Temporal Investigations how he and his crew went back in time to when Captain James Kirk of the first Starship Enterprise exposed a Klingon spy with the help of Tribbles.
Darvin, a disgraced Klingon spy, travels back in time to alter some events to his likings. The DS9 crew must find what he's trying to change and prevent it without altering the time line. They'll have to blend in with the crew from Star Trek: The Original Series.—Jesse Sanchez