For a quarter of a century, mankind has known about the existence of the malignant omega clouds. Huge waves of deadly energy, they seem bent on destroying any civilization they come across.

Now, Earth itself is in the line of fire - though not imminently. An omega is headed toward the planet, but it will not enter the solar system for nine hundred years.

Though research continues into the origin of the omegas and various theoretical scenarios for destroying them are suggested, there is no sense of urgency - until a Space Academy ship on a routine mission sends word back to Earth that the cloud has diverted to a previously unexplored planetary system. It is now aimed at a living pre-technological alien society, only the third such ever discovered - and it will reach the planet in a matter of months. Suddenly, the need to turn theory into practice becomes vital, as a handful of brave humans, scientists and military alike, undertake the task of saving an entire world without revealing their existence.