In 2268 the Enterprise was passing near to Darren V when it came under attack by a flight of chemically fuelled sublight missiles. The ship easily defeated the attack, and upon backtracking their course it found that the missiles had been fired from a large asteroid. It quickly became apparent that the rock, which measured over three hundred and twenty kilometres in diameter, was in fact travelling under power on an independent course through the system.

Scans revealed that the asteroid was in fact hollow, with a solid inner core. The space between the outer and inner layers was filled with a class M environment, including projections of a sun and stars on a day-night cycle. Captain Kirk led a landing party to the core and found it populated by the Fabrini, a Humanoid species which had built the ship they called Yonada some ten thousand years ago to allow their people to escape a nova which destroyed their planet. The ship was placed under the fully automatic control of a computer system which came to be known as the Oracle. Powered by primitive nuclear engines, the ship was designed to travel over interstellar distances over a period of many thousands of years in order to reach a new planet where the passengers could settle.

Unfortunately, during the voyage the Oracle's programming appears to have become corrupted. It took over complete control of the population, forcing them to accept implants which monitored their opinions and inflicted great pain, or even death, if they did not blindly follow its orders. Over the centuries the Oracle became a religious figure to the Fabrini. It convinced them that their ship was in fact a planet, forbidding any attempt to discover otherwise. Other flaws eventually developed, causing one of the ship's eight drive tubes to go out of alignment.

This knocked the ship off course, sending it directly at Darren V - a planet with a population of 3,724 million people. Despite resistance from the Oracle Captain Kirk and his officers managed to break into the Oracle's data banks and repair the systems in order to allow Yonada to reach its goal successfully in 2270.