A periodic outbreak of permitted riot on Beta III, beginning at the Red Hour, during which the placid followers of Landru give way to violence and abandon.
Festival is the one release granted to the people of Beta III under Landru. For most of their lives the members of the Body are calm and passive. At the Red Hour, six in the evening, they erupt into hours of rioting, vandalism and assault, and at six the next morning they return to their blank calm.
It is seen in The Return of the Archons in 2267. James T. Kirk's landing party beams down just before the Red Hour and takes shelter in a boarding house as the streets descend into chaos. Their host's daughter, Tula, is among those caught up in it.
The custom is among the first signs that this society is being controlled. Kirk eventually discovers that Landru is a computer built six thousand years ago, and he argues it into destroying itself.