Shrouded in eternal gloom by its own thick atmosphere Tenebra was a hostile planet...a place of crushing gravity, 370-degree temperatures, a constantly shifting crust and giant drifting raindrops.

Unpromising - yet there was life, intelligent life on Tenebra. For more than 20 years, Earth scientists had studied the natives from an orbiting laboratory...and had even found a way to train and educate a few of them.

Then the unexpected happened! A young Earth girl and the son of a powerful, hot-tempered alien diplomat were marooned in a bathyscape, drifting toward the planet's deadly surface.

Only the primitive Tenebrans could rescue them!