Divine Extinction — Hylton Smith

They thought that they had engineered temporary respite from the threat to humanity. Four years was a convincing period of inactivity. The vigil was suddenly invaded by fear of a completely different danger, which hovered over the species.
The plot follows the pendulum of breakthrough and setback in dealing with the impending disaster. Contemplation of the consequences was bad enough without the emergence of a deadline, which ironically fosters a most unusual alliance.
It may not be afforded the time to make a difference.