Star Trek: The Original Series. 3 Seasons available with subscription. Start Your Free Trial. Season 1 29 Episodes. Season 2 26 Episodes. Season 3 24. Star Trek: The Original Series - Season 1 The series follows the crew of the starship U.S.S. Enterprise as it completes its missions in space in the 23rd century. Dr. McCoy discovers his old flame is not what she seems after crew members begin dying from a sudden lack of salt in their bodies.