While on a routine supply mission to a colony planet, the U.S.S. Enterprise comes under an attack from an unknown malevolent force. Pike brings all his heart and experience to bear in facing the crisis, but the security officer warns him that the enemy cannot be dealt with by conventional Starfleet means.

Uhura seems to be the only one who can hear a strange sound. When the noise triggers terrifying hallucinations, she enlists an unlikely assistant to help her track down the source.