From the Grave: The Prayer by William Castle

Trade paperback format.  By the famed B-movie director himself!

As the Gypsies gather in the ancient village of Les-Saintes-Maries-de-la-Mer for the annual celebration honoring their patron saint, a mystical convergence of events brings four adolescents together at a haunted house and sets them on a perilous quest to locate a centuries-old manuscript that holds the power to release the devastating force of the Ancient Ones upon the Earth.

Fifteen-year-old Sarah and her younger brother Luca are lonely Gypsy kids who travel about Europe with their parents. Forced by their Gypsy father to beg and pick pockets for money, Sarah and Luca find it impossible to earn their father's approval. Fifteen-year-old Edgar cannot stand his parents (and the feeling is mutual) when the family moves from New Jersey to France so that his parents can live out their dream of being French aristocracy.

Fourteen-year-old Aleck's world is turned upside down when his parents are killed in a car crash and his older sister decides that he would be better off in France with their Aunt and Uncle whose real concern is their own lavish lifestyle. Beset by their parents and guardians, the four young people must also survive the mercurial activities of a spirit haunting the house that holds clues to the location of the manuscript which is also sought by a secret society bent on locating it for their own purposes.

In a frenzied chase that takes them from the ancient villages of Provence through the blood-soaked quarries of Roussillon to the macabre catacombs of Paris, the four must put aside their differences and suspicions to outwit the evil forces who would stop at nothing to get their hands on the ancient book. "From the Grave: The Prayer" is a classic tale of terror, suspense and intrigue set in southern France, written by the Master of the Macabre, William Castle.