Uhura's Song (Star Trek: The Original Series #21)

Years ago, Lieutenant Uhura befriended a diplomat from Eeiauo, a land of graceful, catlike beings. The two women exchanged forbidden songs and promised never to reveal their secret. Now the Starship Enterprise must race to save the Eeiauoans before a deadly plague destroys them all. 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 Kirk must crack the code before the Enterprise succumbs!