Say you're sorry (Little, Brown Book Group)

My name is Piper Hadley and I went missing on the last Saturday of the summer holidays three years ago. When Piper and her friend Tash disappeared, there was a huge police search, but they were never found. Now Tash, reaching breaking point at the abuse their captor has inflicted on them, has escaped, promising to come back for Piper. Clinical psychologist Joe O'Loughlin and his stalwart companion, ex-cop Vincent Ruiz, force the police to re-open the case after Joe is called in to assess the possible killer of a couple in their own home and finds a connection to the missing girls. But they are racing against time to save Piper from someone with an evil, calculating and twisted mind.