The boy in the shadows Danny katz series, book 1.

1970: In an overcrowded Stockholm subway station, a harried father and his two boys are late for their train. Joel, the youngest, is howling in his stroller and his seven-year-old brother, Kristoffer, refuses to take the elevator. A woman approaches and helpfully offers to lead Kristoffer up the stairs. Reluctantly his father agrees, but when he arrives on the platform Kristoffer and the woman have vanished without a trace. The kidnapping become...