The fourth episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Bruce Hyde guest stars as Lt. Kevin Riley. 
Stardate 1704.2: A member of a landing party investigating the ruins on a collapsing planet contracts an unknown infection and returns it to the Enterprise, where it spreads rapidly by touch. Lt. Riley locks himself in engineering and shuts down the engines, which may be needed to get the ship away to avoid damage from the planet’s impending destruction. Kirk slowly begins to lose control, and even Spock is affected by the infection, while the planet’s final phase of collapse begins with very little warning.
written by John D.F. Black
directed by Marc Daniels
music by Alexander CourageCast: William Shatner (Captain James T. Kirk), Leonard Nimoy (Mr. Spock), Stewart Moss (Tormolen), Majel Barrett (Christine), Bruce Hyde (Riley), DeForest Kelley (Dr. McCoy), Grace Lee Whitney (Yeoman Rand), George Takei (Sulu), James Doohan (Scott), Nichelle Nichols (Uhura), William Knight (Amorous Crewman), John Bellah (Laughing Crewman)
LogBook entry by Earl Green