MYSTERIES: Children, concealments, codgers, companions.

Byline: Jay Strafford

Jul. 1--When a mystery of the past collides with one of the present, sparks fly and pages turn themselves. Such is the case with the smashing debut novel of Tana French, In the Woods (464 pages, Viking, $24.95).

When he was 12, Rob Ryan and two friends were playing in the woods near their homes in a developing area outside Dublin. The friends vanished, and Rob was found nearly catatonic, his socks and shoes soaked with blood.

Fast-forward 20-plus years. The case is cold, and Rob is a homicide detective near his old haunts. He and his partner, Cassie Maddox, are assigned to the case of Katy Devlin, a 12-year-old girl found murdered in the same woods. The investigation goes nowhere until a …