In the slums of London, she'll do almost anything to survive ...

London, 1810. Margaret Forsythe never expected to become a condom maker. But she is a widow, and due to her late husband's careless will, she has lost everything. Now she has been exiled to the filth of Southwark, with no money or means of survival.

Never again will she be beholden to a man. But when her situation becomes dire, she has little choice but to throw herself on the mercy of the dangerously handsome brothel owner, Charles Grimsby.

Charles's prostitutes need condoms (or 'johnny caps') to avoid venereal disease - and so, torn between morality and poverty, Margaret begins to manufacture them, using animal gut and ribbons. Will this new enterprise be her salvation, or her ultimate ruin?