When a landing party beams down to the planet Gamma Trianguli VI, they find what appears to be an idyllic paradise. They quickly discover, however, that the planet is deadly, sporting plants that shoot thorns, rocks that explode, and incredibly accurate lightning bolts. They encounter the planet's inhabitants, a peaceful, child-like people who call themselves the "Feeders of Vaal." Vaal seems to be a large serpent's head carved of rock, but is actually the terminal for an advanced, underground computer.

Keith Andes (Akuta)
Celeste Yarnell (Yeoman Martha Landon)
James Doohan (Lt. Cmdr. Montgomery Scott)
David Soul (Makora)
Walter Koenig (Ensign Pavel Chekov)
Jay Jones (Ensign Mallory)
Jerry Daniels (Marple)
John Winston (Lt. Kyle)
Mal Friedman (Hendorff)
Shari Nims (Sayana)

• Kirk and Scott don't seem overly concerned for the first dead "red-shirt" security officer. After Kirk reports the death, Scott says that he heard it's nice down on the planet and would love to come down to walk around! By the end of the episode, all four security red-shirts are dead.
  
• Spock notes that destroying Vaal would violate the Prime Directive. Kirk ignores him.
  
• Curiously, the tropical climate of Gamma Trianguli VI reminds Chekov of his home country, Russia.