An accelerated-aging disease is traced to a genetic experiment.
The Enterprise answers a distress call from the starship Lantree, which is found with its entire crew dead from rapid old age. Soon after, the Enterprise visits the Darwin Genetic Research Station, where children have been genetically engineered with enhanced abilities. The station's staff seems nervous, and the children have a disturbing, hidden power.
Dr. Pulaski is infected and begins to age rapidly herself, so the crew is in a race against time to find a cure. The episode is a thoughtful but grim look at genetic engineering and the risk of playing with human biology. Pulaski's fate adds to the tension, and the resolution relies on a clever use of the transporter system.