Hanging Hill by Mo Hayder
What if you found yourself divorced and penniless? With no skills and a teenage daughter to support? What if the only way to survive was to do things you never thought possible, to go places you never knew existed...These are questions Sally has never really thought about before. Married to a successful business man, she's always been a bit of a dreamer. Until now. Her sister Zoe is her polar opposite. A detective inspector working out of Bath Central, she loves her job, and oozes self-confidence. No one would guess that she hides a crippling secret that dates back twenty years, and which - if exposed - may destroy her. Then Sally's daughter gets into difficulties, and Sally finds she needs cash - lots of it - fast. With no one to help her, she is forced into a criminal world of extreme pornography and illegal drugs; a world in which teenage girls can go missing. Two sisters intent on survival. Until one does something so terrifying that there's no way back...