1936. West Yorkshire is home to a gleaming brand-new telephone exchange where Cynthia Norma and Millicent work the complicated electrical switchboards. They relish the independence and friendship their jobs have given them. But when a colleague connects a telephone call and listens in to the conversation - breaking one of the telephonists' main rules - the three women become caught up in a story of scandal corruption and murder. Soon all their jobs are on the line. In tough times the telephone girls will need to call on their friends more than ever.