Harry Bosch works cold cases as a volunteer for the San Fernando police department when he's called out to a local drug store where a young pharmacist has been murdered. Bosch and the town's three-person detective squad sift through the clues, which lead into the dangerous, big business world of prescription drug abuse.
Meanwhile, an old case from Bosch's LAPD days comes back to haunt him when a long-imprisoned killer claims Harry framed him and that there's new evidence which proves it. Bosch left the LAPD on bad terms, so his former colleagues aren't keen to protect his reputation. He must fend for himself in clearing his name and keeping a clever killer in prison.
The two unrelated cases wind across each other like strands of barbed wire, and Bosch learns that there are two kinds of truth: the kind that sets you free and the kind that leaves you buried in darkness.