Earth is long since dead. On a colony planet, a band of men has gained control of technology, made themselves immortal, and now rules their world as the gods of the Hindu pantheon. Only one dares oppose them: he who was once Siddhartha and is now Mahasamatman. Binder of Demons, Lord of Light.

At first, only a few things are known about the celestial object that astronomers dub Rama. It is huge, weighing more than ten trillion tons. And it is hurtling through the solar system at an inconceivable speed. Then a space probe confirms the unthinkable: Rama is no natural object. It is, incredibly, an interstellar spacecraft. Space explorers and planet-bound scientists alike prepare for mankind's first encounter with alien intelligence. It will kindle their wildest dreams... and fan their darkest fears. For no one knows who the Ramans are or why they have come. And now the moment of rendezvous awaits — just behind a Raman airlock door.

In the twenty-second century, Earth obtains limitless, free energy from a source science little understands: an exchange between Earth and a parallel universe, using a process devised by the aliens. But even free energy has a price. The transference process itself will eventually lead to the destruction of the Earth's Sun—and of Earth itself.

Only a few know the terrifying truth—an outcast Earth scientist, a rebellious alien inhabitant of a dying planet, a lunar-born human intuitionist who senses the imminent annihilation of the Sun. They know the truth—but who will listen? They have foreseen the cost of abundant energy—but who will believe? These few beings, human and alien, hold the key to the Earth's survival.