"Turn back! Danger ahead!" The thundering voice, detached from any visible person, transfixes Kay Tracey as the warning fills the sky with a sinister echo. When the eerie reverberations die, the teen-age detective and her chums, Betty and Wilma Worth, look at one another in horror.

What is the source of the spine-chilling threat that suddenly casts a shadow of fear on the gay outing? Similar weird occurrences have struck panic into other vacationists at Lost Lake, and could cause the resort to be abandoned, with great loss to friends of Kay. From the beginning of her stay at the Worths' cottage, Kay is determined to pierce the veil of mystery that envelops the community.

For one thing, she has made up her mind to assist kindly, gentle, old Mr. Nelson in his quest for a long-lost family fortune in Faraway Valley. Then, there is beautiful Hilda Arno, whose strange plight also has touched Kay's heart. The young woman is depending on the girl detective for help.

Although Betty and Wilma are fearful, Kay feels she must dare the challenge of this nerve-tingling mystery. But little does she dream of the terrifying web of danger that lies ahead, waiting to engulf her if she should make one false step.