To the purple born, the key to life on Earth is the DNA helix, which determines all the characteristics of every living thing. The helix, a series of molecules within the life cell, is a spiral - with a left-hand turn. The planet called Dextra could have been a duplicate of Earth. It teemed with life, both flora and fauna. But on Dextra the helix of life had a right-hand thread. And there could be no viable combination between the two life forms, the native and the invading Terran. So it became a battle on the part of the colonists to uproot the native Dextran ecology - purple plants and beasts with surprising intelligence - and replace it with Earth-born green. But the planet fought back in its own way. And the result is a science fiction novel that is unusual, exciting, and highly original.