Stardate: 52.2--While exploring the Delta Triangle, where many starships have disappeared, the Enterprise is attacked by several Klingon vessels.
original airdate--November 24,1973
Goofs: Sulu falls out of his chair, but at the very next change of camera angle (an overhead shot of the entire bridge) he is seen still sitting in his chair.
- Spock states the sensors are not reliable. Then they see a Klingon ship that fires on Enterprise. Enterprise returns fire and the Klingon vanishes. Spock says that the Klingon's shields clearly deflected the phasers, nor did it cloak. He then says the sensors are still not working properly. If the sensors weren't working properly Spock would have no way of knowing any of this.