An American Agent by Jacqueline Winspear
Private investigator Maisie and her friend Priscilla spend a few evenings a week driving an ambulance in London during the blitz. Catherine Saxon, an American reporter, rides along one night, reports what she saw on the radio, and is found dead the next day. Maisie and her assistant Billy investigate, with occasional help from an attractive American agent, Mark Scott. Maisie visits Catherine’s boarding house, and meets with her friends, all while worried about her family in Kent, where she spends weekends. An intriguing puzzle, appealing characters, and a fast-paced story make this a memorable mystery. The first book in the long-running series is Maisie Dobbs.