CONKLIN PARKED OUR CAR on the narrow, tree-lined road in Monterey, a small coastal town two hours south of San Francisco. On my right, one wing of the three-story, wood-frame house remained untouched, while the center of the house had burned out to the framing timbers, the roof open to the blue sky like a silent scream.

  Conklin and I pushed through the clumps of sidewalk gawkers, ducked under the barricade tape, and loped up the walk.

  The arson investigator was waiting for us outside the front door. He was in his early thirties, over six feet tall, jangling the keys and change in his pocket. He introduced himself as Ramon Jimenez and gave me his card with his cell phone number printed on the back. Jimenez opened the fire department lock on the front door so we could enter the center of the house, and as the front door swung open we were hit with the smell of apples and cinnamon.

  “Air freshener explosion,” Jimenez said. “The crispy critters were found in the den.”

  As we followed Jimenez into the fire-ravaged shell, I thought about how some cops and firefighters use jargon to show that they’re tough - when in fact they’re horrified. Others do it because they get off on it. What kind of guy was Jimenez?

  “Was the front door locked?” I asked him.

  “No, and a neighbor called the fire in. Lots of people don’t bother to set their alarms around here.”

  Broken glass crunched under my shoes and water lapped over the tops of them as I slogged through the open space, trying to get a sense of the victims’ lives from the remains and residue of their home. But my knack for fitting puzzle pieces together was blunted by the extent of the destruction. First the fire, then the water and the mop-up, left the worst kind of crime scene.

  If there had been fingerprints, they were gone. Hair, fiber, blood spatter, footprints, receipts, notes - forget all of that. Unless a bomb trigger or trace of an accelerant was found, we couldn’t even be sure that this fire and the others we were investigating had been set by the same person.

  The mos............