Valley of bones - Michael Gruber

After a Sudanese businessman falls ten stories from his hotel-room balcony, Paz investigates his murder and finds a most unlikely suspect -- an otherworldly creature named Emmylou Dideroff who claims to commune with the holy saints. Her "Confessions", scribbled in a series of notebooks, tell a remarkable tale of a woman from the wrong side of the tracks - thief, drug dealer, prostitute - who would be called into the service of God in a most unusual way. Might this "service" include the killing of the Sudanese businessman, whose knowledge of oil reserves may be contributing to African genocide?

It is left to police psychologist Lorna Wise to determine whether Emmylou is legally insane. But when people associated with her start turning up dead, both Paz and Lorna begin to suspect that there's something much larger at stake than Emmylou's guilt or innocence -- and that the search for justice might bring them up against an even more elemental force ...