From amazon.com:

FBI agent Rachel Walling finally gets the call she's dreaded for years, the one that tells her the Poet has surfaced.  She has never forgotten the serial killer who wove lines of poetry in his hideous crimes--and apparently he has not forgotten her.

Former LAPD detective Harry Bosch gets a call, too--from the widow of an old friend. Her husband's death seems natural, but his ties to the hunt for the Poet make Bosch dig deep.  Arriving at a derelict spot in the California desert where the feds are unearthing bodies, Bosch joins forces with Rachel.  Now the two are at odds with the FBI... and squarely in the path of the Poet, who will lead them on a wicked ride out of the heat, through the narrows of evil, and into a darkness all his own...