Season: 1

Original Airdate:October 6, 1966

Writer(s): Richard Matheson

Director(s):Leo Penn

Guest Stars
Jim Goodwin as Farrell
Edward Madden as Fisher
Eddie Paskey as Connors
Garland Thompson as Wilson
Don Eitner as photo double for Capt. James Kirk

Stardate: 1672.1

Synopsis: A transporter malfunction splits Kirk into good-Kirk and evil-Kirk.