Years ago, Lt. Uhura befriended a diplomat from Eeiauo, the land of graceful, cat-like beings. The two women exchanged forbidden music and promised never to reveal their secret.
Now the USS Enterprise is orbiting Eeiauo in a desperate race to save the inhabitants before a deadly plague destroys them. Uhura's secret songs may hold the key to a cure - but the clues are veiled in layers of mystery. The plague is killing humans, threatening other planets - and Captain Kirk must crack the code before the Enterprise succumbs.