Elise Fraser. The Mystery of the Star Sapphire (1961) 153 pp.
Publisher’s description: “As the lights suddenly went out in the restaurant where he was eating, Bill Whitney desperately clutched the front of his coat where, snugly hidden in a leather wallet, lay fifty thousand dollars’ worth of jewels. Then he grinned to himself. This was not Ratnapura, Ceylon, or some Asian port where thieves stopped at nothing. This was San Francisco. Even so, he breathed with relief as candles were lit throughout the room. But, as gem dealer Sam Rosencranz later told him, Bill seemed to attract trouble. From the night in the restaurant he was a marked man, for it was there that he first saw lovely Avis Draper and her rare cornflower blue star sapphire. She wore the ring casually, yet he could not imagine that its value was unknown to her. Fascinated, he stared at it until he noticed the dark scowl of her escort. As the mysterious events of the following days occurred, Bill became deeper and deeper enmeshed in a sinister plot to rob him of his precious gems. His suspicions were first aroused by a cruel looking man who seemed intent on shadowing him, but it was not until the end of this … mystery that Bill realized how close he came to death, and how God’s purpose was to be fulfilled in his life, and in the life of the gray-eyed girl who wore the star sapphire.”
Setting: San Francisco