Ruth Rendell: Going Wrong (UK 1998)

From the Publisher:
Guy still believed that Leonora loved him, as she had when she was a young girl, when he led a street gang around London's Notting Hill Gate, a world away from her family home in a mews house in Holland Park. Leonora's mother in particular didn't care for her dark-looking boyfriend, especially when she found out about the shoplifting, and the drugs.

Guy's obsession with Leonora increased as the years passed, and as they grew apart. He always believed she would come back to him. But even when Leonora told him it could not be like that, that life was not like a fairy tale, he could not, would not, accept the truth. And a murderous madness began to take hold of him...

Ruth Rendell: Going Wrong. Arrow, ISBN: 0099280337 (June, 1998), 250 p., £5.99