Black Sisters' Street is Zwartezusterstraat, in the middle of Belgium's red-light district, home to four African women who have fled their homeland in the naïve hope of betterment. All have been put there by Dele, a Lagos pimp who gets them out and set up for "taty t'ousand euro", but withholds their passports until they have paid it back. It is rich material for a novel  lost, lonely women with a severe case of culture shock seeking solace in each other  and Unigwe is in some ways up to the task. She has passion, has done her research, and the small pleasures the women indulge in to steel themselves against the indignity of their lives are exquisitely observed and heartbreaking all by themselves. It makes it more frustrating, then, that the male figures are either abusive or weakly passive ciphers. And the girls themselves  memories of childhood tragedies crowding their thoughts, struggling against the cold, sobbing at their first trick  fail to break out of the creative-writing exercise mould of how to portray lonely prostitutes battling against the world.