Star Trek: The Original Series
The Return of the Archons
S1 E21: Searching Beta III for survivors of the USS Archon, Kirk and crew discover a society whose citizens appear to be staid and respectable, until the advent of "Red Hour" allows them to run amok. Kirk and Spock avoid being "absorbed" into the "body" long enough to discover the bizarre source of the planet's unity.
Starring Harry Townes, Torin Thatcher, Karl Held