A PHOENIX COLD CASE: David Mapstone has returned to Phoenix, Arizona, the desert city he left behind a lifetime ago. The ex-cop, ex-history professor is working the police dept's cold case desk, unearthing long-buried secrets. And he's good at it: as an ex-historian Mapstone knows the past is never past, as an ex-cop he knows he can't trust anybody... CONCRETE DESERT: A young woman's body is found dumped in the desert in circumstances identical to those of an infamous 40-year-old unsolved murder. CACTUS HEART: Mapstone unearths the skeletons of a pair of four-year-old twins, the victims in a notorious Depression-era kidnapping case. But what should be a matter of tying up loose ends quickly becomes something more sinister, more personal... and more deadly. CAMELBACK FALLS: When Sheriff Peralta is shot by a sniper, Mapstone must confront the deadly consequences of a small-town shoot-out in 1979 that left Peralta and Mapstone standing over four dead bodies.