The Enterprise crew attempts to stop a plague of amoeba-like creatures from possessing human hosts and spreading throughout the galaxy.
Episode rating
Cast of episode
- Captain James Tiberius 'Jim' Kirk
- Mister Spock
- Dr. McCoy
- Scott
- Aurelan
- Yeoman Zahra
- Nurse Chapel
- Sulu
- Uhura
- Peter
- First Denevan
- Montgomery
- Eminiar Guard
- Lieutenant Hadley
- Berserk Engineer
- Lt. Brent
- Enterprise crewmember
- Yeoman
- Lieutenant Leslie
- Crewman