Isabella Ashton has always been her father's favourite, but when she becomes involved with the new birth control movement, Simeon is scandalised. He tells himself that it will be merely a phase before she settles down to a respectable marriage, but as Bella's enthusiasm for 'fallen women' shows no sign of abating, Simeon loses patience and banished her from the family home. Running a family planning clinic in Salford's mean streets is challenging but rewarding work, and Bella is grateful for the help of Violet Howarth, a generous-hearted woman. Violet's son Dan also supports her mission and comradeship quickly turns into love. But Bella is involved with handsome, ne'er-do-well Billy Quinn, leader of an illegal betting ring. His jealousy and possessiveness brings matters to a head and Bella finds everything she has worked for at risk, and herself in mortal danger...