Meet Me in Monte Carlo — Denise Robins

The boulevards of Paris, Cannes, Monte Carlo --perhaps in their glamour Sylvia could forget Johnny. . . forget that he no longer wanted to marry her. But Sylvia didn't know when she left London that she was about to be plunged into a ring of jewel thieves, that handsome, romantic Henri was a criminal mastermind, and that Johnny would turn up in Dijon with Lucille, who was very stunning and very French.

At the center of the intrigue were stolen emeralds worth half a million dollars. And when those emeralds surfaced in her handbag, Sylvia began the most dangerous adventure of her life--an adventure that would perish all her doubts about Johnny's love.