A six-month distance from the Federation, the planet Belle Terre offers a new life to more than 60,000 families, pioneers, scientists, expatriates, go-getters, loners, and entrepreneurs, all under the watchful eye of Captain Kirk and his crew. But the would-be colonists have barely settled in the untamed wilderness of their new home when Spock makes a startling discovery: not only does one of the planet's moons contain a rare ore of the most inestimable value, that same moon is also violently unstable. Within months, it will inevitable explode -- destroying all life on Belle Terre!