Derleth, August - Sign of Fear (1935)

Christopher Jannichon, archaeologist, has been called back from Peru to his Wisconsin home by a series of strange postcards containing weird markings and ominous warnings. When he arrives home he finds similar markings drawn in the snow on the grounds of the Prairie estate and learns his brother Cornelius has also received similar anonymous postcards with odd symbols. The dominate symbol is described as "a cross topped with a cedilla" (though the illustration on the DJ shows a cross topped with a circumflex), known to both brothers through their extensive reading of Incan culture as the "God-help-us!" sign. It is clear to the Jannichons that someone is threatening them and they speculate it may have to do with Christopher's research in ancient Incan life. They consult with Judge Peck who is invited to stay the weekend when several relatives and friends are planning to visit the two brothers. That night their cousin Edna suffers a mysterious fatal attack. She is found dead on the floor of her bedroom an expression of terror on her face. Beneath her body is a slip of paper with one of the "God-help-us!" symbols drawn in red ink. The threats have come true, but was Edna the intended victim?

For a full review see the post at Pretty Sinister Books.