In 2261, Professor Crater and his wife, Nancy arrived on planet M-113, and established an archaeological dig around some of the ruins on the planet. Over the next four years they exported many fascinating discoveries of the planet, but in 2265, the number of items being exported dwindled immensely when Nancy was killed by the last remaining "salt vampire", although this was not discovered until 2266.
Instead of killing the creature, Crater took pity on the creature and it assumed the shape of Nancy and lived with Crater for a year. However, the truth was revealed in late 2266 when the USS Enterprise arrived to perform routine medical examinations of the Craters'. Initially, Crater continued the pretense that the creature was Nancy, but this unravelled when the creature managed to get aboard the Enterprise and killed several crewmembers. While aboard the Enterprise, Crater was killed by the creature in order to try and keep its identity a secret, but it was eventually killed by Dr. Leonard McCoy when it began to attack Captain James T. Kirk. (TOS episode: "The Man Trap")
- In the novelization of this episode, entitled "The Unreal McCoy" by James Blish, Professor Crater was referred to as Robert Bierce.