Simisola by Ruth Rendell

In the quiet Sussex country town of Kingsmarkham, the daughter of Nigerian physician Raymond Akande is missing. It's probably nothing, says Dr. Akande to his friend and client Chief Inspector Wexford, whose help he enlists.

But the days that follow prove the doctor dreadfully wrong. A young woman is found murdered not Melanie, but the last person to have seen and spoken to her. A second woman's body is discovered, again not Melanie's, but like her, young and black. A third woman turns up beaten and unconscious; like the others, she is of Nigerian origin. As Inspector Wexford's investigation stretches from days into weeks, it becomes his unhappy obligation to counter the hopes of the doctor and his wife. In Wexford's professional opinion, Melanie, like the other young women, has become the victim of a serial killer with a horrifyingly singular objective.