The starship Enterprise is assigned to attend the ceremony that will unite a world. The focus of the ceremony is a pair of Siamese Twins named Abon and Delor who represent the united factions of the planet Nador. Disaster strikes when assassination attempts are made against the twins, who embody the hopes and dreams of the formerly war-torn planet's entire population. Captain James T. Kirk must root out the assassins from whatever hiding places they are striking from - whether they be hidden in deep places or even in plain sight. Meanwhile, Dr. McCoy must perform a radical surgical procedure in a desperate attempt to save Abon and Delor's lives.