''The Secret at the Windmill'' as usual follows the juvenile detective novel follows a teenage amateur sleuth Kay. Created by the Stratemeyer Syndicate, the same group behind Nancy Drew and The Hardy Boys.
Kay Tracey, a clever 16-year-old high school student who solves mysteries, is embroiled in a fast-paced theft and a hidden inheritance. Kay is pinned down and smothered in the dark by an intruder. The thief escapes with a treasure of money that Kay was guarding. To recover the funds, Kay must track down its true owner. The trail involves a ragged old man who originally carried the money and a girl named Juliana Van Camp, whose upcoming wedding relies entirely on uncovering the truth.
