The Paris Spy by Susan Elia MacNeal

Maggie Hope is in Paris, living at the Ritz and working undercover to try and find out if fellow agents working for Britain against the Nazis have been compromised. She is also hoping to find her half-sister, Elise, whom she wants to get to safety in England. It seems a British agent with the code name Gibbon is in cahoots with the Germans and has been passing along anything he learns, endangering Maggie and those close to her. Will Maggie succeed in her mission?   The Paris Spy continues the story of Maggie and her friends amidst the turmoil of World War II.