"That Which Survives" is the seventeenth episode of the third season of the original science fiction television series, Star Trek, first broadcast January 24, 1969, and repeated July 29, 1969. It was written by John Meredyth Lucas, based on a story by D.C. Fontana under the pseudonym Michael Richards and directed by Herb Wallerstein.In this episode, the crew of the Enterprise visit an abandoned outpost guarded by a mysterious computer.