The parallel storylines focusing on two detectives involved in the same search shouldn't have worked as well as it did for as long as it did - its an airport thriller trick and it almost never works at all. But because the reader knew the two cases were linked long before the detectives, we begin to see connections they don't even though their ostensible objectives are different. The different personalities of the detectives also kept it fresh for some time. But it made the climax pretty worthless, just popping back and forth like act breaks in a TV show. A pity because the chase of the macguffins across the two timelines was engaging enough even if simply presented chronologically.