"The Doomsday Machine" is a second-season episode of Star Trek: The Original Series. It is episode #35, production #35, and was first broadcast on October 20, 1967. It was repeated on April 19, 1968. It was written by Norman Spinrad, and directed by Marc Daniels. Overview: The starship Enterprise plays a deadly game of cat-and-mouse with an alien planet-killing machine.