The Night Ferry — Michael Robotham

Ali Barba, a Sikh detective with the Metropolitan Police, is recovering from injuries sustained in the line of duty when she receives a letter from her estranged friend, Cate, imploring her to come to their high school reunion. Alarmed by the urgent tone of the note, and eager to make amends for her unforgivable past behavior, Ali goes to the reunion. Cate is pregnant, but before Ali has the chance to congratulate her, Cate hurriedly whispers, "They want to take my baby. You have to stop them." It is the only hint of Cate's troubles Ali manages to get. As they are leaving the reunion, Cate and her husband are run down by a car and killed. The mystery darkens when it is discovered that Cate had faked her pregnancy by tying a pillow underneath her dress.

All Ali has to go on is a file in Cate's desk that contains two ultrasound pictures, letters from a fertility clinic, and various papers that seem to confirm the unborn baby's existence. As she puts together the pieces, her search takes her to Amsterdam and into the company of some very unsavory people on both sides of the Channel who'll do anything to thwart her investigation.