The U.S.S. Enterprise's mission is to take Lieuenant Mira Romaine to Memory Alpha, the central library for the United Federation of Planets, where she will supervise the transfer of new equipment to the facility. While in orbit, an energy storm destroys all the inhabitants of Memory Alpha, wiping its computer memory banks. The storm enters the Enterprise where it is seen as brilliantly flashing colored lights, which enter Lieutenant Romaine, with no way to remove them without killing the officer. The lights are discovered to be non-corporeal entities from the long-dead planet Zetar.

James Doohan (Lt. Cmdr. Montgomery Scott)
Jan Shutan (Lt. Mira Romaine)
George Takei (Lt. Hikaru Sulu)
Walter Koenig (Ensign Pavel Chekov)
Nichelle Nichols (Lt. Uhura)
Majel Barrett (Nurse Christine Chapel)
John Winston (Lt. Kyle)
Libby Erwin (Technician)