Strange incorporeal aliens threaten the Memory Alpha station and the Enterprise.
Quest roles:
Majel Barrett(Nurse Christine Chapel / Number One / Enterprise Computer (voice)), Frank da Vinci(Lt. Clifford Brent), Barbara Babcock(Lights of Zetar (voice)), John Winston(Lt. Kyle), Roger Holloway(Lt. Lemli (uncredited)), Jan Shutan(Lt. Mira Romaine)