The Intruders by Michael Marshall
Taut, menacing, sinister, gripping, intelligent, action-packed - everything you could want from a thriller. When ex-LAPD patrol cop Jack Whalen's wife goes missing on a routine business trip to Seattle, his world is shaken. Meanwhile, a ten-year-old girl vanishes from a beach in Oregon after an encounter with a sinister stranger - but it gradually becomes clear that she's very far from defenceless. Searching for answers in the shadowy secrets of a past that still haunts him, Jack discovers that the truth has roots deeper and darker than he ever feared.