A Cardassian colony suffering an outbreak of Rudellian plague, the destination of the relief convoy the Defiant is escorting when Worf fires on what appears to be a Klingon civilian transport.
Pentath III is a Cardassian colony world in the Pentath system, close to the Klingon border.
During the Klingon invasion of Cardassian space, the colony is hit by Rudellian plague and the Federation agrees to send medical supplies. In Rules of Engagement, Worf commands the Defiant as escort to the convoy. Klingon warships attack, cloaking and decloaking around the freighters, and Worf orders fire on a vessel that appears ahead, which proves to be a transport said to be carrying 441 civilians.
The Klingon advocate Ch'Pok demands Worf's extradition at a hearing on Deep Space 9. Odo's investigation shows that the passengers had been listed as dead in an earlier crash and that the incident was staged to stop Federation convoys.