1951. Brighton. With the war over and the Nazis brought to justice at Nuremberg, Mirabelle Bevan (Secret Service, retired) thinks her skills are no longer required. After her lover's death she retires to the seaside to put the past behind her and takes a job at a debt collection agency run by the charismatic Big Ben McGuigan. But when the case of Romana Laszlo - a pregnant Hungarian refugee - comes in, Mirabelle soon discovers that her specialist knowledge is vital. With enthusiastic assistance from insurance clerk Vesta Churchill, they follow a mysterious trail of gold sovereigns and corpses that only they can unravel.