On its way to deliver medical supplies to plague-ridden Makus III, the U.S.S. Enterprise passes Murasaki 312. Since they are under Starfleet orders to inspect galactic phenomena such as this quasar-like star group, Spock, McCoy, Scott and four specialists take the shuttlecraft Galileo for a closer look. Unexpectedly, the Galileo is pulled off course and crashes on the planet Taurus II in the center of the Murasake phenomenon. Between attacks by the giant, hostile inhabitants and quarrels among themselves, the crew attempts to repair the shuttle and get off the planet.

Don Marshall (Lt. Boma)
DeForest Kelley (Dr. Leonard H. McCoy)
James Doohan (Lt. Cmdr. Montgomery Scott)
George Takei (Lt. Hikaru Sulu)
Nichelle Nichols (Lt. Uhura)
John Crawford (High Commissioner Ferris)
Peter Marko (Lt. Gaetano)
Phyllis Douglas (Yeoman Mears)
Rees Vaughn (Lt. Latimer)
Grant Woods (Lt. Kelowitz)
Buck Maffei (Creature)
David Ross (Transporter Chief)

• With a rank of [Lt.] Commander and many years in Starfleet, it seems odd that this is Spock's first command mission, which he handles poorly until the end.