In the concluding episode of the four-part story "Galaxy 4," time is running out on the planet Galaxy, as it edges even closer to its inevitable destruction. If he hopes to escape with the lives of himself and his traveling companions, the Doctor (William Hartnell) must quickly negotiate a truce between the planet's two warring factions. The climax of the story serves as a logical lead-in to the next episode, "Mission to the Unknown." Written by William Emms, "The Exploding Planet" originally aired on October 2, 1965; this episode apparently no longer exists. ~ Hal Erickson, Rovi