There is a Serpent in Eden is a novel written by Robert Bloch. It was first published in 1979.
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Eden was a paradise...
A luxurious planned community designed for the good life. The only thing that wasn't perfect were the people:
Warren was planning suicide.
Dolly was hitting the bottle.
Roy was dying of cancer.
Emily was insane.
The Norwood's marriage was on the rocks.
All in all, one could say that everything was normal in Eden, until the day the red panel truck entered the gates. By the time anyone noticed it was too late - the serpent was already hidden - and Eden would never be the same again...