The Secret in the Wall

"San Francisco music store owner Inez Stannert agrees to provide financial assistance to boardinghouse proprietor Moira Krause. When the common wall of the abandoned house adjoining Moira's is breached to expand her business, the corpse of a murdered man tumbles out, along with a worn canvas bag holding a fortune in gold coins. Then the locksmith who made the house's unbreakable locks is brutally slain, and the keys vanish. Inez and private detective Wolter Roeland de Bruijn set out to uncover the truth behind the killings."--