It is 1906 and, having spent 10 full years in darkest Africa, Church of England missionary Charles W. Fortescue is summoned to return to England by his bishop.

After being reunited with his long-estranged fiancée, Deborah, Charles travels on to London to hear of the bishop's plans for him. In the greatest city in the world - the centre of empire, no less - there is an ever-increasing problem of degraded morality, particularly in the east end. In short: prostitution.

The bishop tasks Fortescue with establishing a mission within England itself, to save these fallen women from their lives of sin. However, the bishop also tasks Fortescue with raising the necessary funds himself, and Deborah soon sets about writing to every source of wealth in the country to appeal for donations. They soon hear back from one of the richest, a Lady Isobel Ames.

Unfortunately for Charles, his difficulties have yet to truly begin. Lady Ames quickly takes more than a little shine to him, and after struggling to attract women into the mission they establish together, he finds himself offering London's prostitutes more than he had bargained for - and certainly far more than any other church!