1951, Brighton. With the excitement of the war over and the Nazis brought to justice, Mirabelle Bevan, exSecret Service, moves to the seaside to put the past behind her. She takes a job as a secretary at a debt collection agency run by Big Ben McGuigan, but when confronted by the case of Romana Laszlo, a pregnant Hungarian refugee, Mirabelle discovers that her specialist knowledge is vital. With enthusiastic assistance from the pretty insurance clerk down the corridor, Vesta Churchill, Mirabelle follows a mysterious trail of gold sovereigns, betting scams and bodies to a dark corner of Austerity Britain where forces of evil remain.